diff --git a/substrate/Cargo.lock b/substrate/Cargo.lock
index 1f7ede9b8b..0c315da5de 100644
--- a/substrate/Cargo.lock
+++ b/substrate/Cargo.lock
@@ -1610,9 +1610,9 @@ dependencies = [
  "parking_lot 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-primitives 0.1.0",
  "substrate-client 0.1.0",
- "substrate-extrinsic-pool 0.1.0",
  "substrate-keyring 0.1.0",
  "substrate-primitives 0.1.0",
+ "substrate-transaction-pool 0.1.0",
 ]
 
 [[package]]
@@ -2795,23 +2795,6 @@ dependencies = [
  "wasmi 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
-[[package]]
-name = "substrate-extrinsic-pool"
-version = "0.1.0"
-dependencies = [
- "error-chain 0.12.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "futures 0.1.21 (registry+https://github.com/rust-lang/crates.io-index)",
- "log 0.3.9 (registry+https://github.com/rust-lang/crates.io-index)",
- "parity-codec 1.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "parking_lot 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
- "serde 1.0.70 (registry+https://github.com/rust-lang/crates.io-index)",
- "serde_derive 1.0.70 (registry+https://github.com/rust-lang/crates.io-index)",
- "sr-primitives 0.1.0",
- "substrate-keyring 0.1.0",
- "substrate-test-client 0.1.0",
- "transaction-pool 1.13.2 (registry+https://github.com/rust-lang/crates.io-index)",
-]
-
 [[package]]
 name = "substrate-keyring"
 version = "0.1.0"
@@ -2956,10 +2939,10 @@ dependencies = [
  "sr-version 0.1.0",
  "substrate-client 0.1.0",
  "substrate-executor 0.1.0",
- "substrate-extrinsic-pool 0.1.0",
  "substrate-primitives 0.1.0",
  "substrate-state-machine 0.1.0",
  "substrate-test-client 0.1.0",
+ "substrate-transaction-pool 0.1.0",
  "tokio 0.1.7 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -3005,13 +2988,13 @@ dependencies = [
  "substrate-client 0.1.0",
  "substrate-client-db 0.1.0",
  "substrate-executor 0.1.0",
- "substrate-extrinsic-pool 0.1.0",
  "substrate-keystore 0.1.0",
  "substrate-network 0.1.0",
  "substrate-primitives 0.1.0",
  "substrate-rpc 0.1.0",
  "substrate-rpc-servers 0.1.0",
  "substrate-telemetry 0.3.0",
+ "substrate-transaction-pool 0.1.0",
  "target_info 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "tokio 0.1.7 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -3096,6 +3079,23 @@ dependencies = [
  "substrate-primitives 0.1.0",
 ]
 
+[[package]]
+name = "substrate-transaction-pool"
+version = "0.1.0"
+dependencies = [
+ "error-chain 0.12.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "futures 0.1.21 (registry+https://github.com/rust-lang/crates.io-index)",
+ "log 0.3.9 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-codec 1.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parking_lot 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde 1.0.70 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde_derive 1.0.70 (registry+https://github.com/rust-lang/crates.io-index)",
+ "sr-primitives 0.1.0",
+ "substrate-keyring 0.1.0",
+ "substrate-test-client 0.1.0",
+ "transaction-pool 1.13.2 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "subtle"
 version = "0.5.1"
diff --git a/substrate/Cargo.toml b/substrate/Cargo.toml
index 1f345b3bd8..cabd3e22dc 100644
--- a/substrate/Cargo.toml
+++ b/substrate/Cargo.toml
@@ -26,7 +26,7 @@ members = [
 	"core/client",
 	"core/client/db",
 	"core/executor",
-	"core/extrinsic-pool",
+	"core/transaction-pool",
 	"core/keyring",
 	"core/misbehavior-check",
 	"core/network",
diff --git a/substrate/core/cli/src/informant.rs b/substrate/core/cli/src/informant.rs
index eacc95c50d..eb2cc4617d 100644
--- a/substrate/core/cli/src/informant.rs
+++ b/substrate/core/cli/src/informant.rs
@@ -38,7 +38,7 @@ pub fn start<C>(service: &Service<C>, exit: ::exit_future::Exit, handle: TaskExe
 
 	let network = service.network();
 	let client = service.client();
-	let txpool = service.extrinsic_pool();
+	let txpool = service.transaction_pool();
 	let mut last_number = None;
 
 	let mut sys = System::new();
@@ -98,7 +98,7 @@ pub fn start<C>(service: &Service<C>, exit: ::exit_future::Exit, handle: TaskExe
 		Ok(())
 	});
 
-	let txpool = service.extrinsic_pool();
+	let txpool = service.transaction_pool();
 	let display_txpool_import = txpool.import_notification_stream().for_each(move |_| {
 		let status = txpool.light_status();
 		telemetry!("txpool.import"; "mem_usage" => status.mem_usage, "count" => status.transaction_count, "sender" => status.senders);
diff --git a/substrate/core/client/src/client.rs b/substrate/core/client/src/client.rs
index 5c27887376..350d51fead 100644
--- a/substrate/core/client/src/client.rs
+++ b/substrate/core/client/src/client.rs
@@ -21,7 +21,7 @@ use futures::sync::mpsc;
 use parking_lot::{Mutex, RwLock};
 use primitives::AuthorityId;
 use runtime_primitives::{bft::Justification, generic::{BlockId, SignedBlock, Block as RuntimeBlock}};
-use runtime_primitives::traits::{Block as BlockT, Header as HeaderT, Zero, One, As, NumberFor};
+use runtime_primitives::traits::{Block as BlockT, Header as HeaderT, Zero, One, As, NumberFor, GetHeight, BlockNumberToHash};
 use runtime_primitives::BuildStorage;
 use primitives::{Blake2Hasher, RlpCodec, H256};
 use primitives::storage::{StorageKey, StorageData};
@@ -568,6 +568,29 @@ impl<B, E, Block> Client<B, E, Block> where
 	}
 }
 
+impl<B, E, Block> GetHeight for Client<B, E, Block> where
+	B: backend::Backend<Block, Blake2Hasher, RlpCodec>,
+	E: CallExecutor<Block, Blake2Hasher, RlpCodec> + Clone,
+	Block: BlockT,
+{
+	type BlockNumber = <Block::Header as HeaderT>::Number;
+	fn get_height(&self) -> Self::BlockNumber {
+		self.backend.blockchain().info().map(|i| i.best_number).unwrap_or_else(|_| Zero::zero())
+	}
+}
+
+impl<B, E, Block> BlockNumberToHash for Client<B, E, Block> where
+	B: backend::Backend<Block, Blake2Hasher, RlpCodec>,
+	E: CallExecutor<Block, Blake2Hasher, RlpCodec> + Clone,
+	Block: BlockT,
+{
+	type BlockNumber = <Block::Header as HeaderT>::Number;
+	type Hash = Block::Hash;
+	fn block_number_to_hash(&self, n: Self::BlockNumber) -> Option<Self::Hash> {
+		self.block_hash(n).unwrap_or(None)
+	}
+}
+
 impl<B, E, Block> bft::BlockImport<Block> for Client<B, E, Block>
 	where
 		B: backend::Backend<Block, Blake2Hasher, RlpCodec>,
diff --git a/substrate/core/rpc/Cargo.toml b/substrate/core/rpc/Cargo.toml
index d9fec2e4e2..8830f628fe 100644
--- a/substrate/core/rpc/Cargo.toml
+++ b/substrate/core/rpc/Cargo.toml
@@ -13,7 +13,7 @@ parking_lot = "0.4"
 parity-codec = { version = "1.1" }
 substrate-client = { path = "../client" }
 substrate-executor = { path = "../executor" }
-substrate-extrinsic-pool = { path = "../extrinsic-pool" }
+substrate-transaction-pool = { path = "../transaction-pool" }
 substrate-primitives = { path = "../primitives" }
 sr-primitives = { path = "../sr-primitives" }
 sr-version = { path = "../sr-version" }
diff --git a/substrate/core/rpc/src/author/error.rs b/substrate/core/rpc/src/author/error.rs
index e831770056..b3374676e6 100644
--- a/substrate/core/rpc/src/author/error.rs
+++ b/substrate/core/rpc/src/author/error.rs
@@ -17,14 +17,14 @@
 //! Authoring RPC module errors.
 
 use client;
-use extrinsic_pool;
+use transaction_pool;
 use rpc;
 
 use errors;
 
 error_chain! {
 	links {
-		Pool(extrinsic_pool::Error, extrinsic_pool::ErrorKind) #[doc = "Pool error"];
+		Pool(transaction_pool::Error, transaction_pool::ErrorKind) #[doc = "Pool error"];
 		Client(client::error::Error, client::error::ErrorKind) #[doc = "Client error"];
 	}
 	errors {
diff --git a/substrate/core/rpc/src/author/mod.rs b/substrate/core/rpc/src/author/mod.rs
index 5ba5140c5e..c54fe01d8b 100644
--- a/substrate/core/rpc/src/author/mod.rs
+++ b/substrate/core/rpc/src/author/mod.rs
@@ -20,7 +20,7 @@ use std::sync::Arc;
 
 use client::{self, Client};
 use codec::Decode;
-use extrinsic_pool::{
+use transaction_pool::{
 	Pool,
 	IntoPoolError,
 	ChainApi as PoolChainApi,
diff --git a/substrate/core/rpc/src/author/tests.rs b/substrate/core/rpc/src/author/tests.rs
index e5cdf759da..be15b2341e 100644
--- a/substrate/core/rpc/src/author/tests.rs
+++ b/substrate/core/rpc/src/author/tests.rs
@@ -18,7 +18,7 @@ use super::*;
 
 use std::{sync::Arc, result::Result};
 use codec::Encode;
-use extrinsic_pool::{VerifiedTransaction, scoring, Transaction, ChainApi, Error as PoolError,
+use transaction_pool::{VerifiedTransaction, scoring, Transaction, ChainApi, Error as PoolError,
 	Readiness, ExtrinsicFor, VerifiedFor};
 use test_client::runtime::{Block, Extrinsic, Transfer};
 use test_client;
diff --git a/substrate/core/rpc/src/lib.rs b/substrate/core/rpc/src/lib.rs
index a62c789551..b9254cc1a7 100644
--- a/substrate/core/rpc/src/lib.rs
+++ b/substrate/core/rpc/src/lib.rs
@@ -25,7 +25,7 @@ extern crate jsonrpc_pubsub;
 extern crate parking_lot;
 extern crate parity_codec as codec;
 extern crate substrate_client as client;
-extern crate substrate_extrinsic_pool as extrinsic_pool;
+extern crate substrate_transaction_pool as transaction_pool;
 extern crate substrate_primitives as primitives;
 extern crate sr_primitives as runtime_primitives;
 extern crate substrate_state_machine as state_machine;
diff --git a/substrate/core/service/Cargo.toml b/substrate/core/service/Cargo.toml
index 189b3c0b18..2d1a90bab8 100644
--- a/substrate/core/service/Cargo.toml
+++ b/substrate/core/service/Cargo.toml
@@ -25,7 +25,7 @@ substrate-client = { path = "../../core/client" }
 substrate-client-db = { path = "../../core/client/db" }
 parity-codec = { version = "1.1" }
 substrate-executor = { path = "../../core/executor" }
-substrate-extrinsic-pool = { path = "../../core/extrinsic-pool" }
+substrate-transaction-pool = { path = "../../core/transaction-pool" }
 substrate-rpc = { path = "../../core/rpc" }
 substrate-rpc-servers = { path = "../../core/rpc-servers" }
 substrate-telemetry = { path = "../../core/telemetry" }
diff --git a/substrate/core/service/src/components.rs b/substrate/core/service/src/components.rs
index 38088b9050..9badaa49fb 100644
--- a/substrate/core/service/src/components.rs
+++ b/substrate/core/service/src/components.rs
@@ -26,7 +26,7 @@ use client::{self, Client};
 use error;
 use network::{self, OnDemand};
 use substrate_executor::{NativeExecutor, NativeExecutionDispatch};
-use extrinsic_pool::{self, Options as ExtrinsicPoolOptions, Pool as ExtrinsicPool};
+use transaction_pool::{self, Options as TransactionPoolOptions, Pool as TransactionPool};
 use runtime_primitives::{traits::Block as BlockT, traits::Header as HeaderT, BuildStorage};
 use config::Configuration;
 use primitives::{Blake2Hasher, RlpCodec, H256};
@@ -101,13 +101,13 @@ pub type ComponentClient<C> = Client<
 pub type ComponentBlock<C> = <<C as Components>::Factory as ServiceFactory>::Block;
 
 /// Extrinsic hash type for `Components`
-pub type ComponentExHash<C> = <<C as Components>::ExtrinsicPoolApi as extrinsic_pool::ChainApi>::Hash;
+pub type ComponentExHash<C> = <<C as Components>::TransactionPoolApi as transaction_pool::ChainApi>::Hash;
 
 /// Extrinsic type.
 pub type ComponentExtrinsic<C> = <ComponentBlock<C> as BlockT>::Extrinsic;
 
 /// Extrinsic pool API type for `Components`.
-pub type PoolApi<C> = <C as Components>::ExtrinsicPoolApi;
+pub type PoolApi<C> = <C as Components>::TransactionPoolApi;
 
 /// A set of traits for the runtime genesis config.
 pub trait RuntimeGenesis: Serialize + DeserializeOwned + BuildStorage {}
@@ -124,9 +124,9 @@ pub trait ServiceFactory: 'static {
 	/// Chain runtime.
 	type RuntimeDispatch: NativeExecutionDispatch + Send + Sync + 'static;
 	/// Extrinsic pool backend type for the full client.
-	type FullExtrinsicPoolApi: extrinsic_pool::ChainApi<Hash=Self::ExtrinsicHash, Block=Self::Block> + Send + 'static;
+	type FullTransactionPoolApi: transaction_pool::ChainApi<Hash=Self::ExtrinsicHash, Block=Self::Block> + Send + 'static;
 	/// Extrinsic pool backend type for the light client.
-	type LightExtrinsicPoolApi: extrinsic_pool::ChainApi<Hash=Self::ExtrinsicHash, Block=Self::Block> + 'static;
+	type LightTransactionPoolApi: transaction_pool::ChainApi<Hash=Self::ExtrinsicHash, Block=Self::Block> + 'static;
 	/// Genesis configuration for the runtime.
 	type Genesis: RuntimeGenesis;
 	/// Other configuration for service members.
@@ -135,13 +135,13 @@ pub trait ServiceFactory: 'static {
 	/// Network protocol id.
 	const NETWORK_PROTOCOL_ID: network::ProtocolId;
 
-	//TODO: replace these with a constructor trait. that ExtrinsicPool implements.
+	//TODO: replace these with a constructor trait. that TransactionPool implements.
 	/// Extrinsic pool constructor for the full client.
-	fn build_full_extrinsic_pool(config: ExtrinsicPoolOptions, client: Arc<FullClient<Self>>)
-		-> Result<ExtrinsicPool<Self::FullExtrinsicPoolApi>, error::Error>;
+	fn build_full_transaction_pool(config: TransactionPoolOptions, client: Arc<FullClient<Self>>)
+		-> Result<TransactionPool<Self::FullTransactionPoolApi>, error::Error>;
 	/// Extrinsic pool constructor for the light client.
-	fn build_light_extrinsic_pool(config: ExtrinsicPoolOptions, client: Arc<LightClient<Self>>)
-		-> Result<ExtrinsicPool<Self::LightExtrinsicPoolApi>, error::Error>;
+	fn build_light_transaction_pool(config: TransactionPoolOptions, client: Arc<LightClient<Self>>)
+		-> Result<TransactionPool<Self::LightTransactionPoolApi>, error::Error>;
 
 	/// Build network protocol.
 	fn build_network_protocol(config: &FactoryFullConfiguration<Self>)
@@ -157,7 +157,7 @@ pub trait Components: 'static {
 	/// Client executor.
 	type Executor: 'static + client::CallExecutor<FactoryBlock<Self::Factory>, Blake2Hasher, RlpCodec> + Send + Sync;
 	/// Extrinsic pool type.
-	type ExtrinsicPoolApi: 'static + extrinsic_pool::ChainApi<Hash=<Self::Factory as ServiceFactory>::ExtrinsicHash, Block=FactoryBlock<Self::Factory>>;
+	type TransactionPoolApi: 'static + transaction_pool::ChainApi<Hash=<Self::Factory as ServiceFactory>::ExtrinsicHash, Block=FactoryBlock<Self::Factory>>;
 
 	/// Create client.
 	fn build_client(
@@ -170,8 +170,8 @@ pub trait Components: 'static {
 		), error::Error>;
 
 	/// Create extrinsic pool.
-	fn build_extrinsic_pool(config: ExtrinsicPoolOptions, client: Arc<ComponentClient<Self>>)
-		-> Result<ExtrinsicPool<Self::ExtrinsicPoolApi>, error::Error>;
+	fn build_transaction_pool(config: TransactionPoolOptions, client: Arc<ComponentClient<Self>>)
+		-> Result<TransactionPool<Self::TransactionPoolApi>, error::Error>;
 }
 
 /// A struct that implement `Components` for the full client.
@@ -183,7 +183,7 @@ impl<Factory: ServiceFactory> Components for FullComponents<Factory> {
 	type Factory = Factory;
 	type Executor = FullExecutor<Factory>;
 	type Backend = FullBackend<Factory>;
-	type ExtrinsicPoolApi = <Factory as ServiceFactory>::FullExtrinsicPoolApi;
+	type TransactionPoolApi = <Factory as ServiceFactory>::FullTransactionPoolApi;
 
 	fn build_client(
 		config: &FactoryFullConfiguration<Factory>,
@@ -202,10 +202,10 @@ impl<Factory: ServiceFactory> Components for FullComponents<Factory> {
 		Ok((Arc::new(client_db::new_client(db_settings, executor, &config.chain_spec, config.execution_strategy)?), None))
 	}
 
-	fn build_extrinsic_pool(config: ExtrinsicPoolOptions, client: Arc<ComponentClient<Self>>)
-		-> Result<ExtrinsicPool<Self::ExtrinsicPoolApi>, error::Error>
+	fn build_transaction_pool(config: TransactionPoolOptions, client: Arc<ComponentClient<Self>>)
+		-> Result<TransactionPool<Self::TransactionPoolApi>, error::Error>
 	{
-		Factory::build_full_extrinsic_pool(config, client)
+		Factory::build_full_transaction_pool(config, client)
 	}
 }
 
@@ -222,7 +222,7 @@ impl<Factory: ServiceFactory> Components for LightComponents<Factory>
 	type Factory = Factory;
 	type Executor = LightExecutor<Factory>;
 	type Backend = LightBackend<Factory>;
-	type ExtrinsicPoolApi = <Factory as ServiceFactory>::LightExtrinsicPoolApi;
+	type TransactionPoolApi = <Factory as ServiceFactory>::LightTransactionPoolApi;
 
 	fn build_client(
 		config: &FactoryFullConfiguration<Factory>,
@@ -248,9 +248,9 @@ impl<Factory: ServiceFactory> Components for LightComponents<Factory>
 		Ok((Arc::new(client), Some(fetcher)))
 	}
 
-	fn build_extrinsic_pool(config: ExtrinsicPoolOptions, client: Arc<ComponentClient<Self>>)
-		-> Result<ExtrinsicPool<Self::ExtrinsicPoolApi>, error::Error>
+	fn build_transaction_pool(config: TransactionPoolOptions, client: Arc<ComponentClient<Self>>)
+		-> Result<TransactionPool<Self::TransactionPoolApi>, error::Error>
 	{
-		Factory::build_light_extrinsic_pool(config, client)
+		Factory::build_light_transaction_pool(config, client)
 	}
 }
diff --git a/substrate/core/service/src/config.rs b/substrate/core/service/src/config.rs
index fd0db61f8d..2655a62525 100644
--- a/substrate/core/service/src/config.rs
+++ b/substrate/core/service/src/config.rs
@@ -17,7 +17,7 @@
 //! Service configuration.
 
 use std::net::SocketAddr;
-use extrinsic_pool;
+use transaction_pool;
 use chain_spec::ChainSpec;
 pub use client::ExecutionStrategy;
 pub use network::Roles;
@@ -38,7 +38,7 @@ pub struct Configuration<C, G: Serialize + DeserializeOwned + BuildStorage> {
 	/// Node roles.
 	pub roles: Roles,
 	/// Extrinsic pool configuration.
-	pub extrinsic_pool: extrinsic_pool::Options,
+	pub transaction_pool: transaction_pool::Options,
 	/// Network configuration.
 	pub network: NetworkConfiguration,
 	/// Path to key files.
@@ -77,7 +77,7 @@ impl<C: Default, G: Serialize + DeserializeOwned + BuildStorage> Configuration<C
 			chain_spec,
 			name: Default::default(),
 			roles: Roles::FULL,
-			extrinsic_pool: Default::default(),
+			transaction_pool: Default::default(),
 			network: Default::default(),
 			keystore_path: Default::default(),
 			database_path: Default::default(),
diff --git a/substrate/core/service/src/lib.rs b/substrate/core/service/src/lib.rs
index 56e894a0bd..7ae45b788e 100644
--- a/substrate/core/service/src/lib.rs
+++ b/substrate/core/service/src/lib.rs
@@ -33,7 +33,7 @@ extern crate substrate_executor;
 extern crate substrate_client as client;
 extern crate substrate_client_db as client_db;
 extern crate parity_codec as codec;
-extern crate substrate_extrinsic_pool as extrinsic_pool;
+extern crate substrate_transaction_pool as transaction_pool;
 extern crate substrate_rpc;
 extern crate substrate_rpc_servers as rpc;
 extern crate target_info;
@@ -73,7 +73,7 @@ use codec::{Encode, Decode};
 pub use self::error::{ErrorKind, Error};
 pub use config::{Configuration, Roles, PruningMode};
 pub use chain_spec::ChainSpec;
-pub use extrinsic_pool::{Pool as ExtrinsicPool, Options as ExtrinsicPoolOptions, ChainApi, VerifiedTransaction, IntoPoolError};
+pub use transaction_pool::{Pool as TransactionPool, Options as TransactionPoolOptions, ChainApi, VerifiedTransaction, IntoPoolError};
 pub use client::ExecutionStrategy;
 
 pub use components::{ServiceFactory, FullBackend, FullExecutor, LightBackend,
@@ -88,7 +88,7 @@ pub use components::{ServiceFactory, FullBackend, FullExecutor, LightBackend,
 pub struct Service<Components: components::Components> {
 	client: Arc<ComponentClient<Components>>,
 	network: Option<Arc<components::NetworkService<Components::Factory>>>,
-	extrinsic_pool: Arc<ExtrinsicPool<Components::ExtrinsicPoolApi>>,
+	transaction_pool: Arc<TransactionPool<Components::TransactionPoolApi>>,
 	keystore: Keystore,
 	exit: ::exit_future::Exit,
 	signal: Option<Signal>,
@@ -150,12 +150,12 @@ impl<Components> Service<Components>
 		telemetry!("node.start"; "height" => best_header.number().as_(), "best" => ?best_header.hash());
 
 		let network_protocol = <Components::Factory>::build_network_protocol(&config)?;
-		let extrinsic_pool = Arc::new(
-			Components::build_extrinsic_pool(config.extrinsic_pool, client.clone())?
+		let transaction_pool = Arc::new(
+			Components::build_transaction_pool(config.transaction_pool, client.clone())?
 		);
-		let extrinsic_pool_adapter = ExtrinsicPoolAdapter::<Components> {
+		let transaction_pool_adapter = TransactionPoolAdapter::<Components> {
 			imports_external_transactions: !config.roles == Roles::LIGHT,
-			pool: extrinsic_pool.clone(),
+			pool: transaction_pool.clone(),
 			client: client.clone(),
 		 };
 
@@ -167,7 +167,7 @@ impl<Components> Service<Components>
 			chain: client.clone(),
 			on_demand: on_demand.clone()
 				.map(|d| d as Arc<network::OnDemandService<ComponentBlock<Components>>>),
-			transaction_pool: Arc::new(extrinsic_pool_adapter),
+			transaction_pool: Arc::new(transaction_pool_adapter),
 			specialization: network_protocol,
 		};
 
@@ -177,7 +177,7 @@ impl<Components> Service<Components>
 		{
 			// block notifications
 			let network = network.clone();
-			let txpool = extrinsic_pool.clone();
+			let txpool = transaction_pool.clone();
 
 			let events = client.import_notification_stream()
 				.for_each(move |notification| {
@@ -194,7 +194,7 @@ impl<Components> Service<Components>
 		{
 			// extrinsic notifications
 			let network = network.clone();
-			let events = extrinsic_pool.import_notification_stream()
+			let events = transaction_pool.import_notification_stream()
 				// TODO [ToDr] Consider throttling?
 				.for_each(move |_| {
 					network.trigger_repropagate();
@@ -218,7 +218,7 @@ impl<Components> Service<Components>
 				let client = client.clone();
 				let chain = rpc::apis::chain::Chain::new(client.clone(), task_executor.clone());
 				let state = rpc::apis::state::State::new(client.clone(), task_executor.clone());
-				let author = rpc::apis::author::Author::new(client.clone(), extrinsic_pool.clone(), task_executor.clone());
+				let author = rpc::apis::author::Author::new(client.clone(), transaction_pool.clone(), task_executor.clone());
 				rpc::rpc_handler::<ComponentBlock<Components>, ComponentExHash<Components>, _, _, _, _, _>(
 					state,
 					chain,
@@ -262,7 +262,7 @@ impl<Components> Service<Components>
 		Ok(Service {
 			client: client,
 			network: Some(network),
-			extrinsic_pool: extrinsic_pool,
+			transaction_pool: transaction_pool,
 			signal: Some(signal),
 			keystore: keystore,
 			exit,
@@ -283,8 +283,8 @@ impl<Components> Service<Components>
 	}
 
 	/// Get shared extrinsic pool instance.
-	pub fn extrinsic_pool(&self) -> Arc<ExtrinsicPool<Components::ExtrinsicPoolApi>> {
-		self.extrinsic_pool.clone()
+	pub fn transaction_pool(&self) -> Arc<TransactionPool<Components::TransactionPoolApi>> {
+		self.transaction_pool.clone()
 	}
 
 	/// Get shared keystore.
@@ -350,13 +350,13 @@ impl substrate_rpc::system::SystemApi for RpcConfig {
 }
 
 /// Transaction pool adapter.
-pub struct ExtrinsicPoolAdapter<C: Components> {
+pub struct TransactionPoolAdapter<C: Components> {
 	imports_external_transactions: bool,
-	pool: Arc<ExtrinsicPool<C::ExtrinsicPoolApi>>,
+	pool: Arc<TransactionPool<C::TransactionPoolApi>>,
 	client: Arc<ComponentClient<C>>,
 }
 
-impl<C: Components> ExtrinsicPoolAdapter<C> {
+impl<C: Components> TransactionPoolAdapter<C> {
 	fn best_block_id(&self) -> Option<BlockId<ComponentBlock<C>>> {
 		self.client.info()
 			.map(|info| BlockId::hash(info.chain.best_hash))
@@ -367,7 +367,7 @@ impl<C: Components> ExtrinsicPoolAdapter<C> {
 	}
 }
 
-impl<C: Components> network::TransactionPool<ComponentExHash<C>, ComponentBlock<C>> for ExtrinsicPoolAdapter<C> {
+impl<C: Components> network::TransactionPool<ComponentExHash<C>, ComponentBlock<C>> for TransactionPoolAdapter<C> {
 	fn transactions(&self) -> Vec<(ComponentExHash<C>, ComponentExtrinsic<C>)> {
 		let best_block_id = match self.best_block_id() {
 			Some(id) => id,
@@ -398,7 +398,7 @@ impl<C: Components> network::TransactionPool<ComponentExHash<C>, ComponentBlock<
 				Ok(xt) => Some(*xt.hash()),
 				Err(e) => match e.into_pool_error() {
 					Ok(e) => match e.kind() {
-						extrinsic_pool::ErrorKind::AlreadyImported(hash) =>
+						transaction_pool::ErrorKind::AlreadyImported(hash) =>
 							Some(::std::str::FromStr::from_str(&hash).map_err(|_| {})
 								.expect("Hash string is always valid")),
 						_ => {
diff --git a/substrate/core/sr-primitives/src/generic/checked_extrinsic.rs b/substrate/core/sr-primitives/src/generic/checked_extrinsic.rs
index e8be8dd534..05d0fe44a2 100644
--- a/substrate/core/sr-primitives/src/generic/checked_extrinsic.rs
+++ b/substrate/core/sr-primitives/src/generic/checked_extrinsic.rs
@@ -25,10 +25,9 @@ use traits::{self, Member, SimpleArithmetic, MaybeDisplay};
 #[derive(PartialEq, Eq, Clone)]
 #[cfg_attr(feature = "std", derive(Serialize, Deserialize, Debug))]
 pub struct CheckedExtrinsic<AccountId, Index, Call> {
-	/// Who this purports to be from, if anyone (note this is not a signature).
-	pub signed: Option<AccountId>,
-	/// The number of extrinsics have come before from the same signer.
-	pub index: Index,
+	/// Who this purports to be from and the number of extrinsics have come before
+	/// from the same signer, if anyone (note this is not a signature).
+	pub signed: Option<(AccountId, Index)>,
 	/// The function that should be called.
 	pub function: Call,
 }
@@ -44,15 +43,15 @@ where
 	type AccountId = AccountId;
 	type Call = Call;
 
-	fn index(&self) -> &Self::Index {
-		&self.index
+	fn index(&self) -> Option<&Self::Index> {
+		self.signed.as_ref().map(|x| &x.1)
 	}
 
 	fn sender(&self) -> Option<&Self::AccountId> {
-		self.signed.as_ref()
+		self.signed.as_ref().map(|x| &x.0)
 	}
 
 	fn deconstruct(self) -> (Self::Call, Option<Self::AccountId>) {
-		(self.function, self.signed)
+		(self.function, self.signed.map(|x| x.0))
 	}
 }
diff --git a/substrate/core/sr-primitives/src/generic/era.rs b/substrate/core/sr-primitives/src/generic/era.rs
new file mode 100644
index 0000000000..afc4eba13d
--- /dev/null
+++ b/substrate/core/sr-primitives/src/generic/era.rs
@@ -0,0 +1,192 @@
+// Copyright 2017 Parity Technologies (UK) Ltd.
+// This file is part of Substrate.
+
+// Substrate is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Substrate is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Substrate.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Generic implementation of an unchecked (pre-verification) extrinsic.
+
+use codec::{Decode, Encode, Input, Output};
+
+pub type Period = u64;
+pub type Phase = u64;
+
+/// An era to describe the longevity of a transaction.
+#[derive(PartialEq, Eq, Clone, Copy)]
+#[cfg_attr(feature = "std", derive(Serialize, Deserialize, Debug))]
+pub enum Era {
+	/// The transaction is valid forever. The genesis hash must be present in the signed content.
+	Immortal,
+
+	/// Period and phase are encoded:
+	/// - The period of validity from the block hash found in the signing material.
+	/// - The phase in the period that this transaction's lifetime begins (and, importantly,
+	/// implies which block hash is included in the signature material). If the `period` is
+	/// greater than 1 << 12, then it will be a factor of the times greater than 1<<12 that
+	/// `period` is.
+	Mortal(Period, Phase),
+}
+
+/*
+E.g. with period == 4:
+0         10        20        30        40
+0123456789012345678901234567890123456789012
+             |...|
+   authored -/   \- expiry
+phase = 1
+n = Q(current - phase, period) + phase
+*/
+impl Era {
+	/// Create a new era based on a period (which should be a power of two between 4 and 65536 inclusive)
+	/// and a block number on which it should start (or, for long periods, be shortly after the start).
+	pub fn mortal(period: u64, current: u64) -> Self {
+		let period = period.checked_next_power_of_two()
+			.unwrap_or(1 << 16)
+			.max(4)
+			.min(1 << 16);
+		let phase = current % period;
+		let quantize_factor = (period >> 12).max(1);
+		let quantized_phase = phase / quantize_factor * quantize_factor;
+
+		Era::Mortal(period, quantized_phase)
+	}
+
+	/// Create an "immortal" transaction. 
+	pub fn immortal() -> Self {
+		Era::Immortal
+	}
+
+	/// `true` if this is an immortal transaction.
+	pub fn is_immortal(&self) -> bool {
+		match self {
+			Era::Immortal => true,
+			_ => false,
+		}
+	}
+
+	/// Get the block number of the start of the era whose properties this object
+	/// describes that `current` belongs to. 
+	pub fn birth(self, current: u64) -> u64 {
+		match self {
+			Era::Immortal => 0,
+			Era::Mortal(period, phase) => (current - phase) / period * period + phase,
+		}
+	}
+
+	/// Get the block number of the first block at which the era has ended.
+	pub fn death(self, current: u64) -> u64 {
+		match self {
+			Era::Immortal => u64::max_value(),
+			Era::Mortal(period, _) => self.birth(current) + period,
+		}
+	}
+}
+
+impl Encode for Era {
+	fn encode_to<T: Output>(&self, output: &mut T) {
+		match self {
+			Era::Immortal => output.push_byte(0),
+			Era::Mortal(period, phase) => {
+				let quantize_factor = (*period as u64 >> 12).max(1);
+				let encoded = (period.trailing_zeros() - 1).max(1).min(15) as u16 | ((phase / quantize_factor) << 4) as u16;
+				output.push(&encoded);
+			}
+		}
+	}
+}
+
+impl Decode for Era {
+	fn decode<I: Input>(input: &mut I) -> Option<Self> {
+		let first = input.read_byte()?;
+		if first == 0 {
+			Some(Era::Immortal)
+		} else {
+			let encoded = first as u64 + ((input.read_byte()? as u64) << 8);
+			let period = 2 << (encoded % (1 << 4));
+			let quantize_factor = (period >> 12).max(1);
+			let phase = (encoded >> 4) * quantize_factor;
+			if period >= 4 && phase < period {
+				Some(Era::Mortal(period, phase))
+			} else {
+				None
+			}
+		}
+	}
+}
+
+#[cfg(test)]
+mod tests {
+	use super::*;
+
+	#[test]
+	fn immortal_works() {
+		let e = Era::immortal();
+		assert_eq!(e.birth(0), 0);
+		assert_eq!(e.death(0), u64::max_value());
+		assert_eq!(e.birth(1), 0);
+		assert_eq!(e.death(1), u64::max_value());
+		assert_eq!(e.birth(u64::max_value()), 0);
+		assert_eq!(e.death(u64::max_value()), u64::max_value());
+		assert!(e.is_immortal());
+
+		assert_eq!(e.encode(), vec![0u8]);
+		assert_eq!(e, Era::decode(&mut&[0u8][..]).unwrap());
+	}
+
+	#[test]
+	fn mortal_codec_works() {
+		let e = Era::mortal(64, 42);
+		assert!(!e.is_immortal());
+
+		let expected = vec![5 + 42 % 16 * 16, 42 / 16];
+		assert_eq!(e.encode(), expected);
+		assert_eq!(e, Era::decode(&mut&expected[..]).unwrap());
+	}
+
+	#[test]
+	fn long_period_mortal_codec_works() {
+		let e = Era::mortal(32768, 20000);
+
+		let expected = vec![(14 + 2500 % 16 * 16) as u8, (2500 / 16) as u8];
+		assert_eq!(e.encode(), expected);
+		assert_eq!(e, Era::decode(&mut&expected[..]).unwrap());
+	}
+
+	#[test]
+	fn era_initialisation_works() {
+		assert_eq!(Era::mortal(64, 42), Era::Mortal(64, 42));
+		assert_eq!(Era::mortal(32768, 20000), Era::Mortal(32768, 20000));
+		assert_eq!(Era::mortal(200, 513), Era::Mortal(256, 1));
+		assert_eq!(Era::mortal(2, 1), Era::Mortal(4, 1));
+		assert_eq!(Era::mortal(4, 5), Era::Mortal(4, 1));
+	}
+
+	#[test]
+	fn quantised_clamped_era_initialisation_works() {
+		// clamp 1000000 to 65536, quantise 1000001 % 65536 to the nearest 4
+		assert_eq!(Era::mortal(1000000, 1000001), Era::Mortal(65536, 1000001 % 65536 / 4 * 4));
+	}
+
+	#[test]
+	fn mortal_birth_death_works() {
+		let e = Era::mortal(4, 6);
+		for i in 6..10 {
+			assert_eq!(e.birth(i), 6);
+			assert_eq!(e.death(i), 10);
+		}
+
+		// wrong because it's outside of the (current...current + period) range
+		assert_ne!(e.birth(10), 6);
+		assert_ne!(e.birth(5), 6);
+	}
+}
\ No newline at end of file
diff --git a/substrate/core/sr-primitives/src/generic/mod.rs b/substrate/core/sr-primitives/src/generic/mod.rs
index 23907d9f6c..6732722c4d 100644
--- a/substrate/core/sr-primitives/src/generic/mod.rs
+++ b/substrate/core/sr-primitives/src/generic/mod.rs
@@ -19,6 +19,8 @@
 // end::description[]
 
 mod unchecked_extrinsic;
+mod unchecked_mortal_extrinsic;
+mod era;
 mod checked_extrinsic;
 mod header;
 mod block;
@@ -27,6 +29,8 @@ mod digest;
 mod tests;
 
 pub use self::unchecked_extrinsic::UncheckedExtrinsic;
+pub use self::unchecked_mortal_extrinsic::UncheckedMortalExtrinsic;
+pub use self::era::Era;
 pub use self::checked_extrinsic::CheckedExtrinsic;
 pub use self::header::Header;
 pub use self::block::{Block, SignedBlock, BlockId};
diff --git a/substrate/core/sr-primitives/src/generic/unchecked_extrinsic.rs b/substrate/core/sr-primitives/src/generic/unchecked_extrinsic.rs
index c7e3693fbf..4f3a32b34d 100644
--- a/substrate/core/sr-primitives/src/generic/unchecked_extrinsic.rs
+++ b/substrate/core/sr-primitives/src/generic/unchecked_extrinsic.rs
@@ -21,7 +21,7 @@ use std::fmt;
 
 use rstd::prelude::*;
 use codec::{Decode, Encode, Input};
-use traits::{self, Member, SimpleArithmetic, MaybeDisplay};
+use traits::{self, Member, SimpleArithmetic, MaybeDisplay, Lookup};
 use super::CheckedExtrinsic;
 
 /// A extrinsic right from the external world. This is unchecked and so
@@ -29,10 +29,9 @@ use super::CheckedExtrinsic;
 #[derive(PartialEq, Eq, Clone)]
 #[cfg_attr(feature = "std", derive(Serialize, Deserialize))]
 pub struct UncheckedExtrinsic<Address, Index, Call, Signature> {
-	/// The signature and address, if this is a signed extrinsic.
-	pub signature: Option<(Address, Signature)>,
-	/// The number of extrinsics have come before from the same signer.
-	pub index: Index,
+	/// The signature, address and number of extrinsics have come before from
+	/// the same signer, if this is a signed extrinsic.
+	pub signature: Option<(Address, Signature, Index)>,
 	/// The function that should be called.
 	pub function: Call,
 }
@@ -41,17 +40,15 @@ impl<Address, Index, Call, Signature> UncheckedExtrinsic<Address, Index, Call, S
 	/// New instance of a signed extrinsic aka "transaction".
 	pub fn new_signed(index: Index, function: Call, signed: Address, signature: Signature) -> Self {
 		UncheckedExtrinsic {
-			signature: Some((signed, signature)),
-			index,
+			signature: Some((signed, signature, index)),
 			function,
 		}
 	}
 
 	/// New instance of an unsigned extrinsic aka "inherent".
-	pub fn new_unsigned(index: Index, function: Call) -> Self {
+	pub fn new_unsigned(function: Call) -> Self {
 		UncheckedExtrinsic {
 			signature: None,
-			index,
 			function,
 		}
 	}
@@ -62,7 +59,7 @@ impl<Address, Index, Call, Signature> UncheckedExtrinsic<Address, Index, Call, S
 	}
 }
 
-impl<Address, AccountId, Index, Call, Signature, ThisLookup> traits::Checkable<ThisLookup>
+impl<Address, AccountId, Index, Call, Signature, Context> traits::Checkable<Context>
 	for UncheckedExtrinsic<Address, Index, Call, Signature>
 where
 	Address: Member + MaybeDisplay,
@@ -70,27 +67,25 @@ where
 	Call: Encode + Member,
 	Signature: Member + traits::Verify<Signer=AccountId>,
 	AccountId: Member + MaybeDisplay,
-	ThisLookup: FnOnce(Address) -> Result<AccountId, &'static str>,
+	Context: Lookup<Source=Address, Target=AccountId>,
 {
 	type Checked = CheckedExtrinsic<AccountId, Index, Call>;
 
-	fn check_with(self, lookup: ThisLookup) -> Result<Self::Checked, &'static str> {
+	fn check(self, context: &Context) -> Result<Self::Checked, &'static str> {
 		Ok(match self.signature {
-			Some((signed, signature)) => {
-				let payload = (self.index, self.function);
-				let signed = lookup(signed)?;
+			Some((signed, signature, index)) => {
+				let payload = (index, self.function);
+				let signed = context.lookup(signed)?;
 				if !::verify_encoded_lazy(&signature, &payload, &signed) {
 					return Err("bad signature in extrinsic")
 				}
 				CheckedExtrinsic {
-					signed: Some(signed),
-					index: payload.0,
+					signed: Some((signed, payload.0)),
 					function: payload.1,
 				}
 			}
 			None => CheckedExtrinsic {
 				signed: None,
-				index: self.index,
 				function: self.function,
 			},
 		})
@@ -114,7 +109,6 @@ where
 
 		Some(UncheckedExtrinsic {
 			signature: Decode::decode(input)?,
-			index: Decode::decode(input)?,
 			function: Decode::decode(input)?,
 		})
 	}
@@ -136,7 +130,6 @@ where
 		v.extend(&[0u8; 4]);
 
 		self.signature.encode_to(&mut v);
-		self.index.encode_to(&mut v);
 		self.function.encode_to(&mut v);
 
 		let length = (v.len() - 4) as u32;
@@ -154,6 +147,6 @@ impl<Address, Index, Call, Signature> fmt::Debug for UncheckedExtrinsic<Address,
 	Call: fmt::Debug,
 {
 	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-		write!(f, "UncheckedExtrinsic({:?}, {:?}, {:?})", self.signature.as_ref().map(|x| &x.0), self.function, self.index)
+		write!(f, "UncheckedExtrinsic({:?}, {:?})", self.signature.as_ref().map(|x| (&x.0, &x.2)), self.function)
 	}
 }
diff --git a/substrate/core/sr-primitives/src/generic/unchecked_mortal_extrinsic.rs b/substrate/core/sr-primitives/src/generic/unchecked_mortal_extrinsic.rs
new file mode 100644
index 0000000000..d2565f5f35
--- /dev/null
+++ b/substrate/core/sr-primitives/src/generic/unchecked_mortal_extrinsic.rs
@@ -0,0 +1,278 @@
+// Copyright 2017 Parity Technologies (UK) Ltd.
+// This file is part of Substrate.
+
+// Substrate is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Substrate is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Substrate.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Generic implementation of an unchecked (pre-verification) extrinsic.
+
+#[cfg(feature = "std")]
+use std::fmt;
+
+use rstd::prelude::*;
+use codec::{Decode, Encode, Input};
+use traits::{self, Member, SimpleArithmetic, MaybeDisplay, GetHeight, BlockNumberToHash, Lookup,
+	Checkable};
+use super::{CheckedExtrinsic, Era};
+
+const TRANSACTION_VERSION: u8 = 1;
+
+/// A extrinsic right from the external world. This is unchecked and so
+/// can contain a signature.
+#[derive(PartialEq, Eq, Clone)]
+#[cfg_attr(feature = "std", derive(Serialize, Deserialize))]
+pub struct UncheckedMortalExtrinsic<Address, Index, Call, Signature> {
+	/// The signature, address, number of extrinsics have come before from
+	/// the same signer and an era describing the longevity of this transaction,
+	/// if this is a signed extrinsic.
+	pub signature: Option<(Address, Signature, Index, Era)>,
+	/// The function that should be called.
+	pub function: Call,
+}
+
+impl<Address, Index, Call, Signature> UncheckedMortalExtrinsic<Address, Index, Call, Signature> {
+	/// New instance of a signed extrinsic aka "transaction".
+	pub fn new_signed(index: Index, function: Call, signed: Address, signature: Signature, era: Era) -> Self {
+		UncheckedMortalExtrinsic {
+			signature: Some((signed, signature, index, era)),
+			function,
+		}
+	}
+
+	/// New instance of an unsigned extrinsic aka "inherent".
+	pub fn new_unsigned(function: Call) -> Self {
+		UncheckedMortalExtrinsic {
+			signature: None,
+			function,
+		}
+	}
+
+	/// `true` if there is a signature.
+	pub fn is_signed(&self) -> bool {
+		self.signature.is_some()
+	}
+}
+
+impl<Address, AccountId, Index, Call, Signature, Context, Hash, BlockNumber> Checkable<Context>
+	for UncheckedMortalExtrinsic<Address, Index, Call, Signature>
+where
+	Address: Member + MaybeDisplay,
+	Index: Encode + Member + MaybeDisplay + SimpleArithmetic,
+	Call: Encode + Member,
+	Signature: Member + traits::Verify<Signer=AccountId>,
+	AccountId: Member + MaybeDisplay,
+	BlockNumber: SimpleArithmetic,
+	Hash: Encode,
+	Context: Lookup<Source=Address, Target=AccountId>
+		+ GetHeight<BlockNumber=BlockNumber>
+		+ BlockNumberToHash<BlockNumber=BlockNumber, Hash=Hash>,
+{
+	type Checked = CheckedExtrinsic<AccountId, Index, Call>;
+
+	fn check(self, context: &Context) -> Result<Self::Checked, &'static str> {
+		Ok(match self.signature {
+			Some((signed, signature, index, era)) => {
+				let h = context.block_number_to_hash(BlockNumber::sa(era.birth(context.get_height().as_())))
+					.ok_or("transaction birth block ancient")?;
+				let payload = (index, self.function, h);
+				let signed = context.lookup(signed)?;
+				if !::verify_encoded_lazy(&signature, &payload, &signed) {
+					return Err("bad signature in extrinsic")
+				}
+				CheckedExtrinsic {
+					signed: Some((signed, payload.0)),
+					function: payload.1,
+				}
+			}
+			None => CheckedExtrinsic {
+				signed: None,
+				function: self.function,
+			},
+		})
+	}
+}
+
+impl<Address, Index, Call, Signature> Decode
+	for UncheckedMortalExtrinsic<Address, Index, Call, Signature>
+where
+	Address: Decode,
+	Signature: Decode,
+	Index: Decode,
+	Call: Decode,
+{
+	fn decode<I: Input>(input: &mut I) -> Option<Self> {
+		// This is a little more complicated than usual since the binary format must be compatible
+		// with substrate's generic `Vec<u8>` type. Basically this just means accepting that there
+		// will be a prefix of u32, which has the total number of bytes following (we don't need
+		// to use this).
+		let _length_do_not_remove_me_see_above: u32 = Decode::decode(input)?;
+
+		let version = input.read_byte()?;
+
+		let is_signed = version & 0b1000_0000 != 0;
+		let version = version & 0b0111_1111;
+		if version != TRANSACTION_VERSION {
+			return None
+		}
+
+		Some(UncheckedMortalExtrinsic {
+			signature: if is_signed { Some(Decode::decode(input)?) } else { None },
+			function: Decode::decode(input)?,
+		})
+	}
+}
+
+impl<Address, Index, Call, Signature> Encode
+	for UncheckedMortalExtrinsic<Address, Index, Call, Signature>
+where
+	Address: Encode,
+	Signature: Encode,
+	Index: Encode,
+	Call: Encode,
+{
+	fn encode(&self) -> Vec<u8> {
+		let mut v = Vec::new();
+
+		// need to prefix with the total length as u32 to ensure it's binary comptible with
+		// Vec<u8>. we'll make room for it here, then overwrite once we know the length.
+		v.extend(&[0u8; 4]);
+
+		// 1 byte version id.
+		match self.signature.as_ref() {
+			Some(s) => {
+				v.push(TRANSACTION_VERSION | 0b1000_0000);
+				s.encode_to(&mut v);
+			}
+			None => {
+				v.push(TRANSACTION_VERSION & 0b0111_1111);
+			}
+		}
+		self.function.encode_to(&mut v);
+
+		let length = (v.len() - 4) as u32;
+		length.using_encoded(|s| v[0..4].copy_from_slice(s));
+
+		v
+	}
+}
+
+/// TODO: use derive when possible.
+#[cfg(feature = "std")]
+impl<Address, Index, Call, Signature> fmt::Debug for UncheckedMortalExtrinsic<Address, Index, Call, Signature> where
+	Address: fmt::Debug,
+	Index: fmt::Debug,
+	Call: fmt::Debug,
+{
+	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+		write!(f, "UncheckedMortalExtrinsic({:?}, {:?})", self.signature.as_ref().map(|x| (&x.0, &x.2)), self.function)
+	}
+}
+
+#[cfg(test)]
+mod tests {
+	use super::*;
+
+	struct TestContext;
+	impl Lookup for TestContext {
+		type Source = u64;
+		type Target = u64;
+		fn lookup(&self, s: u64) -> Result<u64, &'static str> { Ok(s) }
+	}
+	impl GetHeight for TestContext {
+		type BlockNumber = u64;
+		fn get_height(&self) -> u64 { 42 }
+	}
+	impl BlockNumberToHash for TestContext {
+		type BlockNumber = u64;
+		type Hash = u64;
+		fn block_number_to_hash(&self, n: u64) -> Option<u64> { Some(n) }
+	}
+
+	#[derive(Eq, PartialEq, Clone, Debug, Serialize, Deserialize, Encode, Decode)]
+	struct TestSig(u64, Vec<u8>);
+	impl traits::Verify for TestSig {
+		type Signer = u64;
+		fn verify<L: traits::Lazy<[u8]>>(&self, mut msg: L, signer: &Self::Signer) -> bool {
+			*signer == self.0 && msg.get() == &self.1[..]
+		}
+	}
+
+	const DUMMY_FUNCTION: u64 = 0;
+	const DUMMY_ACCOUNTID: u64 = 0;
+	
+	type Ex = UncheckedMortalExtrinsic<u64, u64, u64, TestSig>;
+	type CEx = CheckedExtrinsic<u64, u64, u64>;
+
+	#[test]
+	fn unsigned_codec_should_work() {
+		let ux = Ex::new_unsigned(DUMMY_FUNCTION);
+		let encoded = ux.encode();
+		assert_eq!(Ex::decode(&mut &encoded[..]), Some(ux));
+	}
+
+	#[test]
+	fn signed_codec_should_work() {
+		let ux = Ex::new_signed(0, DUMMY_FUNCTION, DUMMY_ACCOUNTID, TestSig(DUMMY_ACCOUNTID, (DUMMY_ACCOUNTID, DUMMY_FUNCTION, 0u64).encode()), Era::immortal());
+		let encoded = ux.encode();
+		assert_eq!(Ex::decode(&mut &encoded[..]), Some(ux));
+	}
+
+	#[test]
+	fn unsigned_check_should_work() {
+		let ux = Ex::new_unsigned(DUMMY_FUNCTION);
+		assert!(!ux.is_signed());
+		assert!(<Ex as Checkable<TestContext>>::check(ux, &TestContext).is_ok());
+	}
+
+	#[test]
+	fn badly_signed_check_should_fail() {
+		let ux = Ex::new_signed(0, DUMMY_FUNCTION, DUMMY_ACCOUNTID, TestSig(DUMMY_ACCOUNTID, vec![0u8]), Era::immortal());
+		assert!(ux.is_signed());
+		assert_eq!(<Ex as Checkable<TestContext>>::check(ux, &TestContext), Err("bad signature in extrinsic"));
+	}
+
+	#[test]
+	fn immortal_signed_check_should_work() {
+		let ux = Ex::new_signed(0, DUMMY_FUNCTION, DUMMY_ACCOUNTID, TestSig(DUMMY_ACCOUNTID, (DUMMY_ACCOUNTID, DUMMY_FUNCTION, 0u64).encode()), Era::immortal());
+		assert!(ux.is_signed());
+		assert_eq!(<Ex as Checkable<TestContext>>::check(ux, &TestContext), Ok(CEx { signed: Some((DUMMY_ACCOUNTID, 0)), function: DUMMY_FUNCTION }));
+	}
+
+	#[test]
+	fn mortal_signed_check_should_work() {
+		let ux = Ex::new_signed(0, DUMMY_FUNCTION, DUMMY_ACCOUNTID, TestSig(DUMMY_ACCOUNTID, (DUMMY_ACCOUNTID, DUMMY_FUNCTION, 42u64).encode()), Era::mortal(32, 42));
+		assert!(ux.is_signed());
+		assert_eq!(<Ex as Checkable<TestContext>>::check(ux, &TestContext), Ok(CEx { signed: Some((DUMMY_ACCOUNTID, 0)), function: DUMMY_FUNCTION }));
+	}
+
+	#[test]
+	fn later_mortal_signed_check_should_work() {
+		let ux = Ex::new_signed(0, DUMMY_FUNCTION, DUMMY_ACCOUNTID, TestSig(DUMMY_ACCOUNTID, (DUMMY_ACCOUNTID, DUMMY_FUNCTION, 11u64).encode()), Era::mortal(32, 11));
+		assert!(ux.is_signed());
+		assert_eq!(<Ex as Checkable<TestContext>>::check(ux, &TestContext), Ok(CEx { signed: Some((DUMMY_ACCOUNTID, 0)), function: DUMMY_FUNCTION }));
+	}
+
+	#[test]
+	fn too_late_mortal_signed_check_should_fail() {
+		let ux = Ex::new_signed(0, DUMMY_FUNCTION, DUMMY_ACCOUNTID, TestSig(DUMMY_ACCOUNTID, (DUMMY_ACCOUNTID, DUMMY_FUNCTION, 10u64).encode()), Era::mortal(32, 10));
+		assert!(ux.is_signed());
+		assert_eq!(<Ex as Checkable<TestContext>>::check(ux, &TestContext), Err("bad signature in extrinsic"));
+	}
+
+	#[test]
+	fn too_early_mortal_signed_check_should_fail() {
+		let ux = Ex::new_signed(0, DUMMY_FUNCTION, DUMMY_ACCOUNTID, TestSig(DUMMY_ACCOUNTID, (DUMMY_ACCOUNTID, DUMMY_FUNCTION, 43u64).encode()), Era::mortal(32, 43));
+		assert!(ux.is_signed());
+		assert_eq!(<Ex as Checkable<TestContext>>::check(ux, &TestContext), Err("bad signature in extrinsic"));
+	}
+}
\ No newline at end of file
diff --git a/substrate/core/sr-primitives/src/testing.rs b/substrate/core/sr-primitives/src/testing.rs
index 7426161cb7..539c58be39 100644
--- a/substrate/core/sr-primitives/src/testing.rs
+++ b/substrate/core/sr-primitives/src/testing.rs
@@ -123,7 +123,7 @@ pub struct TestXt<Call>(pub Option<u64>, pub u64, pub Call);
 
 impl<Call: Codec + Sync + Send + Serialize, Context> Checkable<Context> for TestXt<Call> {
 	type Checked = Self;
-	fn check_with(self, _: Context) -> Result<Self::Checked, &'static str> { Ok(self) }
+	fn check(self, _: &Context) -> Result<Self::Checked, &'static str> { Ok(self) }
 }
 impl<Call> Applyable for TestXt<Call> where
 	Call: 'static + Sized + Send + Sync + Clone + Eq + Codec + Debug + Serialize + DeserializeOwned,
@@ -132,7 +132,7 @@ impl<Call> Applyable for TestXt<Call> where
 	type Index = u64;
 	type Call = Call;
 	fn sender(&self) -> Option<&u64> { self.0.as_ref() }
-	fn index(&self) -> &u64 { &self.1 }
+	fn index(&self) -> Option<&u64> { self.0.as_ref().map(|_| &self.1) }
 	fn deconstruct(self) -> (Self::Call, Option<Self::AccountId>) {
 		(self.2, self.0)
 	}
diff --git a/substrate/core/sr-primitives/src/traits.rs b/substrate/core/sr-primitives/src/traits.rs
index f2be877e59..c7453e02bf 100644
--- a/substrate/core/sr-primitives/src/traits.rs
+++ b/substrate/core/sr-primitives/src/traits.rs
@@ -60,7 +60,33 @@ pub trait Lookup {
 	/// Type to lookup into.
 	type Target;
 	/// Attempt a lookup.
-	fn lookup(s: Self::Source) -> result::Result<Self::Target, &'static str>;
+	fn lookup(&self, s: Self::Source) -> result::Result<Self::Target, &'static str>;
+}
+
+/// Get the "current" block number.
+pub trait GetHeight {
+	/// The type of the block number.
+	type BlockNumber;
+
+	/// Return the current block number. Not allowed to fail.
+	fn get_height(&self) -> Self::BlockNumber;
+}
+
+/// Translate a block number into a hash.
+pub trait BlockNumberToHash {
+	/// The type of the block number.
+	type BlockNumber: Zero;
+
+	/// The type of the hash.
+	type Hash;
+
+	/// Get the hash for a given block number, or `None` if unknown.
+	fn block_number_to_hash(&self, n: Self::BlockNumber) -> Option<Self::Hash>;
+
+	/// Get the genesis block hash; this should always be known.
+	fn genesis_hash(&self) -> Self::Hash {
+		self.block_number_to_hash(Zero::zero()).expect("All blockchains must know their genesis block hash; qed")
+	}
 }
 
 /// Simple payment making trait, operating on a single generic `AccountId` type.
@@ -407,10 +433,11 @@ pub type NumberFor<B> = <<B as Block>::Header as Header>::Number;
 /// Implement for pieces of information that require some additional context `Context` in order to be
 /// checked.
 pub trait Checkable<Context>: Sized {
-	/// Returned if `check_with` succeeds.
+	/// Returned if `check` succeeds.
 	type Checked;
 
-	fn check_with(self, context: Context) -> Result<Self::Checked, &'static str>;
+	/// Check self, given an instance of Context.
+	fn check(self, c: &Context) -> Result<Self::Checked, &'static str>;
 }
 
 /// A "checkable" piece of information, used by the standard Substrate Executive in order to
@@ -421,13 +448,14 @@ pub trait BlindCheckable: Sized {
 	/// Returned if `check` succeeds.
 	type Checked;
 
+	/// Check self.
 	fn check(self) -> Result<Self::Checked, &'static str>;
 }
 
-// Every `BlindCheckable` is also a `Checkable` for arbitrary `Context`.
+// Every `BlindCheckable` is also a `StaticCheckable` for arbitrary `Context`.
 impl<T: BlindCheckable, Context> Checkable<Context> for T {
 	type Checked = <Self as BlindCheckable>::Checked;
-	fn check_with(self, _: Context) -> Result<Self::Checked, &'static str> {
+	fn check(self, _c: &Context) -> Result<Self::Checked, &'static str> {
 		BlindCheckable::check(self)
 	}
 }
@@ -442,7 +470,7 @@ pub trait Applyable: Sized + Send + Sync {
 	type AccountId: Member + MaybeDisplay;
 	type Index: Member + MaybeDisplay + SimpleArithmetic;
 	type Call: Member;
-	fn index(&self) -> &Self::Index;
+	fn index(&self) -> Option<&Self::Index>;
 	fn sender(&self) -> Option<&Self::AccountId>;
 	fn deconstruct(self) -> (Self::Call, Option<Self::AccountId>);
 }
diff --git a/substrate/core/extrinsic-pool/Cargo.toml b/substrate/core/transaction-pool/Cargo.toml
similarity index 92%
rename from substrate/core/extrinsic-pool/Cargo.toml
rename to substrate/core/transaction-pool/Cargo.toml
index 427fd96463..2e476c5171 100644
--- a/substrate/core/extrinsic-pool/Cargo.toml
+++ b/substrate/core/transaction-pool/Cargo.toml
@@ -1,5 +1,5 @@
 [package]
-name = "substrate-extrinsic-pool"
+name = "substrate-transaction-pool"
 version = "0.1.0"
 authors = ["Parity Technologies <admin@parity.io>"]
 
diff --git a/substrate/core/extrinsic-pool/README.adoc b/substrate/core/transaction-pool/README.adoc
similarity index 87%
rename from substrate/core/extrinsic-pool/README.adoc
rename to substrate/core/transaction-pool/README.adoc
index e128d64c9b..48052d0fde 100644
--- a/substrate/core/extrinsic-pool/README.adoc
+++ b/substrate/core/transaction-pool/README.adoc
@@ -1,5 +1,5 @@
 
-= extrinsic-pool
+= transaction-pool
 
 .Summary
 [source, toml]
diff --git a/substrate/core/extrinsic-pool/src/error.rs b/substrate/core/transaction-pool/src/error.rs
similarity index 100%
rename from substrate/core/extrinsic-pool/src/error.rs
rename to substrate/core/transaction-pool/src/error.rs
diff --git a/substrate/core/extrinsic-pool/src/lib.rs b/substrate/core/transaction-pool/src/lib.rs
similarity index 100%
rename from substrate/core/extrinsic-pool/src/lib.rs
rename to substrate/core/transaction-pool/src/lib.rs
diff --git a/substrate/core/extrinsic-pool/src/listener.rs b/substrate/core/transaction-pool/src/listener.rs
similarity index 92%
rename from substrate/core/extrinsic-pool/src/listener.rs
rename to substrate/core/transaction-pool/src/listener.rs
index 8badb331a5..42ad6ef1c3 100644
--- a/substrate/core/extrinsic-pool/src/listener.rs
+++ b/substrate/core/transaction-pool/src/listener.rs
@@ -76,15 +76,15 @@ impl<H, T> txpool::Listener<T> for Listener<H> where
 	}
 
 	fn rejected(&mut self, tx: &Arc<T>, reason: &txpool::ErrorKind) {
-		warn!(target: "extrinsic-pool", "Extrinsic rejected ({}): {:?}", reason, tx);
+		warn!(target: "transaction-pool", "Extrinsic rejected ({}): {:?}", reason, tx);
 	}
 
 	fn invalid(&mut self, tx: &Arc<T>) {
-		warn!(target: "extrinsic-pool", "Extrinsic invalid: {:?}", tx);
+		warn!(target: "transaction-pool", "Extrinsic invalid: {:?}", tx);
 	}
 
 	fn canceled(&mut self, tx: &Arc<T>) {
-		debug!(target: "extrinsic-pool", "Extrinsic canceled: {:?}", tx);
+		debug!(target: "transaction-pool", "Extrinsic canceled: {:?}", tx);
 	}
 
 	fn culled(&mut self, tx: &Arc<T>) {
diff --git a/substrate/core/extrinsic-pool/src/pool.rs b/substrate/core/transaction-pool/src/pool.rs
similarity index 99%
rename from substrate/core/extrinsic-pool/src/pool.rs
rename to substrate/core/transaction-pool/src/pool.rs
index 642171b376..f812a5e544 100644
--- a/substrate/core/extrinsic-pool/src/pool.rs
+++ b/substrate/core/transaction-pool/src/pool.rs
@@ -133,7 +133,7 @@ pub struct Ready<'a, 'b, B: 'a + ChainApi> {
 impl<'a, 'b, B: ChainApi> txpool::Ready<VerifiedFor<B>> for Ready<'a, 'b, B> {
 	fn is_ready(&mut self, xt: &VerifiedFor<B>) -> Readiness {
 		if self.rotator.ban_if_stale(&self.now, xt) {
-			debug!(target: "extrinsic-pool", "[{:?}] Banning as stale.", txpool::VerifiedTransaction::hash(xt));
+			debug!(target: "transaction-pool", "[{:?}] Banning as stale.", txpool::VerifiedTransaction::hash(xt));
 			return Readiness::Stale;
 		}
 
diff --git a/substrate/core/extrinsic-pool/src/rotator.rs b/substrate/core/transaction-pool/src/rotator.rs
similarity index 100%
rename from substrate/core/extrinsic-pool/src/rotator.rs
rename to substrate/core/transaction-pool/src/rotator.rs
diff --git a/substrate/core/extrinsic-pool/src/watcher.rs b/substrate/core/transaction-pool/src/watcher.rs
similarity index 100%
rename from substrate/core/extrinsic-pool/src/watcher.rs
rename to substrate/core/transaction-pool/src/watcher.rs
diff --git a/substrate/doc/packages/substrate.adoc b/substrate/doc/packages/substrate.adoc
index 153900d783..ee246d0909 100644
--- a/substrate/doc/packages/substrate.adoc
+++ b/substrate/doc/packages/substrate.adoc
@@ -15,7 +15,7 @@ include::../../environmental/README.adoc[]
 
 include::../../core/executor/README.adoc[]
 
-include::../../core/extrinsic-pool/README.adoc[]
+include::../../core/transaction-pool/README.adoc[]
 
 include::../../core/keyring/README.adoc[]
 
diff --git a/substrate/node/api/src/lib.rs b/substrate/node/api/src/lib.rs
index aee45ac81d..01945537eb 100644
--- a/substrate/node/api/src/lib.rs
+++ b/substrate/node/api/src/lib.rs
@@ -31,10 +31,9 @@ use client::backend::Backend;
 use client::block_builder::BlockBuilder as ClientBlockBuilder;
 use client::{Client, CallExecutor};
 use primitives::{
-	AccountId, Block, BlockId, Hash, Index, InherentData,
-	SessionKey, Timestamp, UncheckedExtrinsic
+	AccountId, Block, BlockId, BlockNumber, Hash, Index, InherentData, SessionKey, Timestamp, UncheckedExtrinsic
 };
-use sr_primitives::transaction_validity::TransactionValidity;
+use sr_primitives::{transaction_validity::TransactionValidity, traits::{GetHeight, BlockNumberToHash}};
 use substrate_primitives::{Blake2Hasher, RlpCodec};
 
 /// Build new blocks.
@@ -49,7 +48,7 @@ pub trait BlockBuilder {
 /// Trait encapsulating the node API.
 ///
 /// All calls should fail when the exact runtime is unknown.
-pub trait Api {
+pub trait Api: GetHeight<BlockNumber=BlockNumber> + BlockNumberToHash<BlockNumber=BlockNumber,Hash=Hash> {
 	/// The block builder for this API type.
 	type BlockBuilder: BlockBuilder;
 
@@ -91,7 +90,7 @@ pub trait Api {
 impl<B, E> BlockBuilder for ClientBlockBuilder<B, E, Block, Blake2Hasher, RlpCodec>
 where
 	B: Backend<Block, Blake2Hasher, RlpCodec>,
-	E: CallExecutor<Block, Blake2Hasher, RlpCodec>+ Clone,
+	E: CallExecutor<Block, Blake2Hasher, RlpCodec> + Clone,
 {
 	fn push_extrinsic(&mut self, extrinsic: UncheckedExtrinsic) -> Result<()> {
 		self.push(extrinsic).map_err(Into::into)
diff --git a/substrate/node/consensus/src/lib.rs b/substrate/node/consensus/src/lib.rs
index a807ad69a7..ecb57943ee 100644
--- a/substrate/node/consensus/src/lib.rs
+++ b/substrate/node/consensus/src/lib.rs
@@ -48,6 +48,7 @@ use std::time::{self, Duration, Instant};
 use codec::{Decode, Encode};
 use node_api::Api;
 use node_primitives::{AccountId, Hash, Block, BlockId, BlockNumber, Header, Timestamp, SessionKey};
+use runtime_primitives::generic::Era;
 use primitives::{AuthorityId, ed25519};
 use transaction_pool::TransactionPool;
 use tokio::runtime::TaskExecutor;
@@ -400,14 +401,13 @@ impl<C> bft::Proposer<Block> for Proposer<C>
 						=> MisbehaviorKind::BftDoubleCommit(round as u32, (h1, s1.signature), (h2, s2.signature)),
 				}
 			};
-			let payload = (next_index, Call::Consensus(ConsensusCall::report_misbehavior(report)));
+			let payload = (next_index, Call::Consensus(ConsensusCall::report_misbehavior(report)), self.client.genesis_hash());
 			let signature = self.local_key.sign(&payload.encode()).into();
 			next_index += 1;
 
 			let local_id = self.local_key.public().0.into();
 			let extrinsic = UncheckedExtrinsic {
-				signature: Some((node_runtime::RawAddress::Id(local_id), signature)),
-				index: payload.0,
+				signature: Some((node_runtime::RawAddress::Id(local_id), signature, payload.0, Era::immortal())),
 				function: payload.1,
 			};
 			let uxt: GenericExtrinsic = Decode::decode(&mut extrinsic.encode().as_slice()).expect("Encoded extrinsic is valid");
diff --git a/substrate/node/executor/src/lib.rs b/substrate/node/executor/src/lib.rs
index 6c4ee9de3e..aa43e4e65e 100644
--- a/substrate/node/executor/src/lib.rs
+++ b/substrate/node/executor/src/lib.rs
@@ -54,7 +54,7 @@ mod tests {
 		ed25519::{Public, Pair}};
 	use node_primitives::{Hash, BlockNumber, AccountId};
 	use runtime_primitives::traits::{Header as HeaderT, Digest as DigestT};
-	use runtime_primitives::{generic, ApplyOutcome, ApplyError, ApplyResult};
+	use runtime_primitives::{generic, generic::Era, ApplyOutcome, ApplyError, ApplyResult};
 	use {balances, staking, session, system, consensus, timestamp, treasury};
 	use system::{EventRecord, Phase};
 	use node_runtime::{Header, Block, UncheckedExtrinsic, CheckedExtrinsic, Call, Runtime, Balances,
@@ -63,6 +63,7 @@ mod tests {
 
 	const BLOATY_CODE: &[u8] = include_bytes!("../../runtime/wasm/target/wasm32-unknown-unknown/release/node_runtime.wasm");
 	const COMPACT_CODE: &[u8] = include_bytes!("../../runtime/wasm/target/wasm32-unknown-unknown/release/node_runtime.compact.wasm");
+	const GENESIS_HASH: [u8; 32] = [69u8; 32];
 
 	// TODO: move into own crate.
 	macro_rules! map {
@@ -81,19 +82,17 @@ mod tests {
 
 	fn sign(xt: CheckedExtrinsic) -> UncheckedExtrinsic {
 		match xt.signed {
-			Some(signed) => {
-				let payload = (xt.index, xt.function);
+			Some((signed, index)) => {
+				let payload = (index, xt.function, GENESIS_HASH);
 				let pair = Pair::from(Keyring::from_public(Public::from_raw(signed.clone().into())).unwrap());
 				let signature = pair.sign(&payload.encode()).into();
 				UncheckedExtrinsic {
-					signature: Some((balances::address::Address::Id(signed), signature)),
-					index: payload.0,
+					signature: Some((balances::address::Address::Id(signed), signature, payload.0, Era::mortal(256, 0))),
 					function: payload.1,
 				}
 			}
 			None => UncheckedExtrinsic {
 				signature: None,
-				index: xt.index,
 				function: xt.function,
 			},
 		}
@@ -101,8 +100,7 @@ mod tests {
 
 	fn xt() -> UncheckedExtrinsic {
 		sign(CheckedExtrinsic {
-			signed: Some(alice()),
-			index: 0,
+			signed: Some((alice(), 0)),
 			function: Call::Balances(balances::Call::transfer::<Runtime>(bob().into(), 69)),
 		})
 	}
@@ -283,7 +281,7 @@ mod tests {
 	fn block1(support_changes_trie: bool) -> (Vec<u8>, Hash) {
 		construct_block(
 			1,
-			[69u8; 32].into(),
+			GENESIS_HASH.into(),
 			if support_changes_trie {
 				hex!("1755be7303767b4d3855694b4f0ebd9d64b7011124d0ec1ad3e17c2a0d65e245").into()
 			} else {
@@ -297,12 +295,10 @@ mod tests {
 			vec![
 				CheckedExtrinsic {
 					signed: None,
-					index: 0,
 					function: Call::Timestamp(timestamp::Call::set(42)),
 				},
 				CheckedExtrinsic {
-					signed: Some(alice()),
-					index: 0,
+					signed: Some((alice(), 0)),
 					function: Call::Balances(balances::Call::transfer(bob().into(), 69)),
 				},
 			]
@@ -313,22 +309,19 @@ mod tests {
 		construct_block(
 			2,
 			block1(false).1,
-			hex!("29fa1d0aa83662c571315af54b106c73823a31f759793803bf8929960b67b138").into(),
+			hex!("60efe1a65e7c79041b02e56ec122d6eaedfa476e0a9f6f1f68eb0c8f402c4514").into(),
 			None,
 			vec![
 				CheckedExtrinsic {
 					signed: None,
-					index: 0,
 					function: Call::Timestamp(timestamp::Call::set(52)),
 				},
 				CheckedExtrinsic {
-					signed: Some(bob()),
-					index: 0,
+					signed: Some((bob(), 0)),
 					function: Call::Balances(balances::Call::transfer(alice().into(), 5)),
 				},
 				CheckedExtrinsic {
-					signed: Some(alice()),
-					index: 1,
+					signed: Some((alice(), 1)),
 					function: Call::Balances(balances::Call::transfer(bob().into(), 15)),
 				}
 			]
@@ -338,18 +331,16 @@ mod tests {
 	fn block1big() -> (Vec<u8>, Hash) {
 		construct_block(
 			1,
-			[69u8; 32].into(),
+			GENESIS_HASH.into(),
 			hex!("fe0e07c7b054fe186387461d455d536860e9c71d6979fd9dbf755e96ce070d04").into(),
 			None,
 			vec![
 				CheckedExtrinsic {
 					signed: None,
-					index: 0,
 					function: Call::Timestamp(timestamp::Call::set(42)),
 				},
 				CheckedExtrinsic {
-					signed: Some(alice()),
-					index: 0,
+					signed: Some((alice(), 0)),
 					function: Call::Consensus(consensus::Call::remark(vec![0; 120000])),
 				}
 			]
diff --git a/substrate/node/runtime/src/lib.rs b/substrate/node/runtime/src/lib.rs
index 9068d95d35..27e8bc6d4e 100644
--- a/substrate/node/runtime/src/lib.rs
+++ b/substrate/node/runtime/src/lib.rs
@@ -223,11 +223,11 @@ pub type Block = generic::Block<Header, UncheckedExtrinsic>;
 /// BlockId type as expected by this runtime.
 pub type BlockId = generic::BlockId<Block>;
 /// Unchecked extrinsic type as expected by this runtime.
-pub type UncheckedExtrinsic = generic::UncheckedExtrinsic<Address, Index, Call, Signature>;
+pub type UncheckedExtrinsic = generic::UncheckedMortalExtrinsic<Address, Index, Call, Signature>;
 /// Extrinsic type that has already been checked.
 pub type CheckedExtrinsic = generic::CheckedExtrinsic<AccountId, Index, Call>;
 /// Executive: handles dispatch to the various modules.
-pub type Executive = executive::Executive<Runtime, Block, Balances, Balances, AllModules>;
+pub type Executive = executive::Executive<Runtime, Block, balances::ChainContext<Runtime>, Balances, AllModules>;
 
 pub mod api {
 	impl_stubs!(
@@ -251,19 +251,13 @@ pub mod api {
 
 /// Produces the list of inherent extrinsics.
 fn inherent_extrinsics(data: InherentData) -> Vec<UncheckedExtrinsic> {
-	let make_inherent = |function| UncheckedExtrinsic {
-		signature: Default::default(),
-		function,
-		index: 0,
-	};
-
-	let mut inherent = vec![
-		make_inherent(Call::Timestamp(TimestampCall::set(data.timestamp))),
-	];
+	let mut inherent = vec![generic::UncheckedMortalExtrinsic::new_unsigned(
+		Call::Timestamp(TimestampCall::set(data.timestamp))
+	)];
 
 	if !data.offline_indices.is_empty() {
-		inherent.push(make_inherent(
-				Call::Consensus(ConsensusCall::note_offline(data.offline_indices))
+		inherent.push(generic::UncheckedMortalExtrinsic::new_unsigned(
+			Call::Consensus(ConsensusCall::note_offline(data.offline_indices))
 		));
 	}
 
diff --git a/substrate/node/service/src/lib.rs b/substrate/node/service/src/lib.rs
index 469349d1c4..5852ac29f7 100644
--- a/substrate/node/service/src/lib.rs
+++ b/substrate/node/service/src/lib.rs
@@ -50,7 +50,7 @@ use tokio::runtime::TaskExecutor;
 use service::FactoryFullConfiguration;
 use primitives::{Blake2Hasher, RlpCodec};
 
-pub use service::{Roles, PruningMode, ExtrinsicPoolOptions,
+pub use service::{Roles, PruningMode, TransactionPoolOptions,
 	ErrorKind, Error, ComponentBlock, LightComponents, FullComponents};
 pub use client::ExecutionStrategy;
 
@@ -97,20 +97,20 @@ impl service::ServiceFactory for Factory {
 	type ExtrinsicHash = Hash;
 	type NetworkProtocol = DemoProtocol;
 	type RuntimeDispatch = node_executor::Executor;
-	type FullExtrinsicPoolApi = transaction_pool::ChainApi<service::FullClient<Self>>;
-	type LightExtrinsicPoolApi = transaction_pool::ChainApi<service::LightClient<Self>>;
+	type FullTransactionPoolApi = transaction_pool::ChainApi<service::FullClient<Self>>;
+	type LightTransactionPoolApi = transaction_pool::ChainApi<service::LightClient<Self>>;
 	type Genesis = GenesisConfig;
 	type Configuration = CustomConfiguration;
 
 	const NETWORK_PROTOCOL_ID: network::ProtocolId = ::node_network::PROTOCOL_ID;
 
-	fn build_full_extrinsic_pool(config: ExtrinsicPoolOptions, client: Arc<service::FullClient<Self>>)
+	fn build_full_transaction_pool(config: TransactionPoolOptions, client: Arc<service::FullClient<Self>>)
 		-> Result<TransactionPool<service::FullClient<Self>>, Error>
 	{
 		Ok(TransactionPool::new(config, transaction_pool::ChainApi::new(client)))
 	}
 
-	fn build_light_extrinsic_pool(config: ExtrinsicPoolOptions, client: Arc<service::LightClient<Self>>)
+	fn build_light_transaction_pool(config: TransactionPoolOptions, client: Arc<service::LightClient<Self>>)
 		-> Result<TransactionPool<service::LightClient<Self>>, Error>
 	{
 		Ok(TransactionPool::new(config, transaction_pool::ChainApi::new(client)))
@@ -180,7 +180,7 @@ pub fn new_full(config: Configuration, executor: TaskExecutor)
 			client.clone(),
 			client.clone(),
 			consensus_net,
-			service.extrinsic_pool(),
+			service.transaction_pool(),
 			executor,
 			key,
 		))
diff --git a/substrate/node/transaction-pool/Cargo.toml b/substrate/node/transaction-pool/Cargo.toml
index 1d410994f5..2c82b404c8 100644
--- a/substrate/node/transaction-pool/Cargo.toml
+++ b/substrate/node/transaction-pool/Cargo.toml
@@ -13,6 +13,6 @@ node-runtime = { path = "../runtime" }
 substrate-client = { path = "../../core/client" }
 parity-codec = { version = "1.1" }
 substrate-keyring = { path = "../../core/keyring" }
-substrate-extrinsic-pool = { path = "../../core/extrinsic-pool" }
+substrate-transaction-pool = { path = "../../core/transaction-pool" }
 substrate-primitives = { path = "../../core/primitives" }
 sr-primitives = { path = "../../core/sr-primitives" }
diff --git a/substrate/node/transaction-pool/src/error.rs b/substrate/node/transaction-pool/src/error.rs
index 7d1712a55a..6481ad07cd 100644
--- a/substrate/node/transaction-pool/src/error.rs
+++ b/substrate/node/transaction-pool/src/error.rs
@@ -14,14 +14,14 @@
 // You should have received a copy of the GNU General Public License
 // along with Substrate.  If not, see <http://www.gnu.org/licenses/>.
 
-use extrinsic_pool;
+use transaction_pool;
 use node_api;
 use primitives::Hash;
 use runtime::{Address, UncheckedExtrinsic};
 
 error_chain! {
 	links {
-		Pool(extrinsic_pool::Error, extrinsic_pool::ErrorKind);
+		Pool(transaction_pool::Error, transaction_pool::ErrorKind);
 		Api(node_api::Error, node_api::ErrorKind);
 	}
 	errors {
@@ -63,10 +63,10 @@ error_chain! {
 	}
 }
 
-impl extrinsic_pool::IntoPoolError for Error {
-	fn into_pool_error(self) -> ::std::result::Result<extrinsic_pool::Error, Self> {
+impl transaction_pool::IntoPoolError for Error {
+	fn into_pool_error(self) -> ::std::result::Result<transaction_pool::Error, Self> {
 		match self {
-			Error(ErrorKind::Pool(e), c) => Ok(extrinsic_pool::Error(e, c)),
+			Error(ErrorKind::Pool(e), c) => Ok(transaction_pool::Error(e, c)),
 			e => Err(e),
 		}
 	}
diff --git a/substrate/node/transaction-pool/src/lib.rs b/substrate/node/transaction-pool/src/lib.rs
index 44b6ca3d03..5d9db24f45 100644
--- a/substrate/node/transaction-pool/src/lib.rs
+++ b/substrate/node/transaction-pool/src/lib.rs
@@ -16,7 +16,7 @@
 
 extern crate substrate_client as client;
 extern crate parity_codec as codec;
-extern crate substrate_extrinsic_pool as extrinsic_pool;
+extern crate substrate_transaction_pool as transaction_pool;
 extern crate substrate_primitives;
 extern crate sr_primitives;
 extern crate node_runtime as runtime;
@@ -42,20 +42,20 @@ use std::{
 };
 
 use codec::{Decode, Encode};
-use extrinsic_pool::{Readiness, scoring::{Change, Choice}, VerifiedFor, ExtrinsicFor};
+use transaction_pool::{Readiness, scoring::{Change, Choice}, VerifiedFor, ExtrinsicFor};
 use node_api::Api;
-use primitives::{AccountId, BlockId, Block, Hash, Index};
-use runtime::{UncheckedExtrinsic, RawAddress};
-use sr_primitives::traits::{Bounded, Checkable, Hash as HashT, BlakeTwo256};
+use primitives::{AccountId, BlockId, Block, Hash, Index, BlockNumber};
+use runtime::{Address, UncheckedExtrinsic};
+use sr_primitives::traits::{Bounded, Checkable, Hash as HashT, BlakeTwo256, Lookup, GetHeight, BlockNumberToHash};
 
-pub use extrinsic_pool::{Options, Status, LightStatus, VerifiedTransaction as VerifiedTransactionOps};
+pub use transaction_pool::{Options, Status, LightStatus, VerifiedTransaction as VerifiedTransactionOps};
 pub use error::{Error, ErrorKind, Result};
 
 /// Maximal size of a single encoded extrinsic.
 const MAX_TRANSACTION_SIZE: usize = 4 * 1024 * 1024;
 
 /// Type alias for the transaction pool.
-pub type TransactionPool<A> = extrinsic_pool::Pool<ChainApi<A>>;
+pub type TransactionPool<A> = transaction_pool::Pool<ChainApi<A>>;
 
 /// A verified transaction which should be includable and non-inherent.
 #[derive(Clone, Debug)]
@@ -86,7 +86,7 @@ impl VerifiedTransaction {
 	}
 }
 
-impl extrinsic_pool::VerifiedTransaction for VerifiedTransaction {
+impl transaction_pool::VerifiedTransaction for VerifiedTransaction {
 	type Hash = Hash;
 	type Sender = AccountId;
 
@@ -119,8 +119,32 @@ impl<A> ChainApi<A> where
 	}
 }
 
+/// "Chain" context (used for checking transactions) which uses data local to our node/transaction pool.
+///
+/// This is due for removal when #721 lands
+pub struct LocalContext<'a, A: 'a>(&'a Arc<A>);
+impl<'a, A: 'a + Api> GetHeight for LocalContext<'a, A> {
+	type BlockNumber = BlockNumber;
+	fn get_height(&self) -> BlockNumber {
+		self.0.get_height()
+	}
+}
+impl<'a, A: 'a + Api> BlockNumberToHash for LocalContext<'a, A> {
+	type BlockNumber = BlockNumber;
+	type Hash = Hash;
+	fn block_number_to_hash(&self, n: BlockNumber) -> Option<Hash> {
+		self.0.block_number_to_hash(n)
+	}
+}
+impl<'a, A: 'a + Api> Lookup for LocalContext<'a, A> {
+	type Source = Address;
+	type Target = AccountId;
+	fn lookup(&self, a: Address) -> ::std::result::Result<AccountId, &'static str> {
+		self.0.lookup(&BlockId::number(self.get_height()), a).unwrap_or(None).ok_or("error with lookup")
+	}
+}
 
-impl<A> extrinsic_pool::ChainApi for ChainApi<A> where
+impl<A> transaction_pool::ChainApi for ChainApi<A> where
 	A: Api + Send + Sync,
 {
 	type Block = Block;
@@ -145,13 +169,8 @@ impl<A> extrinsic_pool::ChainApi for ChainApi<A> where
 		}
 
 		debug!(target: "transaction-pool", "Transaction submitted: {}", ::substrate_primitives::hexdisplay::HexDisplay::from(&encoded));
-		let checked = uxt.clone().check_with(|a| {
-			match a {
-				RawAddress::Id(id) => Ok(id),
-				RawAddress::Index(_) => Err("Index based addresses are not supported".into()),// TODO: Make index addressing optional in substrate
-			}
-		})?;
-		let sender = checked.signed.expect("Only signed extrinsics are allowed at this point");
+		let checked = uxt.clone().check(&LocalContext(&self.api))?;
+		let (sender, index) = checked.signed.expect("function previously bailed unless uxt.is_signed(); qed");
 
 
 		if encoded_size < 1024 {
@@ -161,7 +180,7 @@ impl<A> extrinsic_pool::ChainApi for ChainApi<A> where
 		}
 
 		Ok(VerifiedTransaction {
-			index: checked.index,
+			index,
 			sender,
 			hash,
 			encoded_size,
@@ -214,7 +233,7 @@ impl<A> extrinsic_pool::ChainApi for ChainApi<A> where
 	}
 
 	fn update_scores(
-		xts: &[extrinsic_pool::Transaction<VerifiedFor<Self>>],
+		xts: &[transaction_pool::Transaction<VerifiedFor<Self>>],
 		scores: &mut [Self::Score],
 		_change: Change<()>
 	) {
diff --git a/substrate/srml/balances/src/lib.rs b/substrate/srml/balances/src/lib.rs
index c56b8d949a..b26904e0fb 100644
--- a/substrate/srml/balances/src/lib.rs
+++ b/substrate/srml/balances/src/lib.rs
@@ -46,7 +46,7 @@ use codec::{Encode, Decode, Codec, Input, Output};
 use runtime_support::{StorageValue, StorageMap, Parameter};
 use runtime_support::dispatch::Result;
 use primitives::traits::{Zero, One, SimpleArithmetic, OnFinalise, MakePayment,
-	As, Lookup, Member, CheckedAdd, CheckedSub};
+	As, Lookup, Member, CheckedAdd, CheckedSub, GetHeight, BlockNumberToHash};
 use address::Address as RawAddress;
 use system::ensure_signed;
 
@@ -630,6 +630,13 @@ impl<T: Trait> Module<T> {
 			<TotalIssuance<T>>::put(v);
 		}
 	}
+
+	pub fn lookup(a: address::Address<T::AccountId, T::AccountIndex>) -> result::Result<T::AccountId, &'static str> {
+		match a {
+			address::Address::Id(i) => Ok(i),
+			address::Address::Index(i) => <Module<T>>::lookup_index(i).ok_or("invalid account index"),
+		}
+	}
 }
 
 impl<T: Trait> OnFinalise<T::BlockNumber> for Module<T> {
@@ -637,14 +644,33 @@ impl<T: Trait> OnFinalise<T::BlockNumber> for Module<T> {
 	}
 }
 
-impl<T: Trait> Lookup for Module<T> {
+pub struct ChainContext<T>(::rstd::marker::PhantomData<T>);
+impl<T> Default for ChainContext<T> {
+	fn default() -> Self {
+		ChainContext(::rstd::marker::PhantomData)
+	}
+}
+
+impl<T: Trait> Lookup for ChainContext<T> {
 	type Source = address::Address<T::AccountId, T::AccountIndex>;
 	type Target = T::AccountId;
-	fn lookup(a: Self::Source) -> result::Result<Self::Target, &'static str> {
-		match a {
-			address::Address::Id(i) => Ok(i),
-			address::Address::Index(i) => <Module<T>>::lookup_index(i).ok_or("invalid account index"),
-		}
+	fn lookup(&self, a: Self::Source) -> result::Result<Self::Target, &'static str> {
+		<Module<T>>::lookup(a)
+	}
+}
+
+impl<T: Trait> GetHeight for ChainContext<T> {
+	type BlockNumber = T::BlockNumber;
+	fn get_height(&self) -> Self::BlockNumber {
+		<system::Module<T>>::block_number()
+	}
+}
+
+impl<T: Trait> BlockNumberToHash for ChainContext<T> {
+	type BlockNumber = T::BlockNumber;
+	type Hash = T::Hash;
+	fn block_number_to_hash(&self, n: Self::BlockNumber) -> Option<Self::Hash> {
+		Some(<system::Module<T>>::block_hash(n))
 	}
 }
 
diff --git a/substrate/srml/council/src/seats.rs b/substrate/srml/council/src/seats.rs
index fd118bca09..a64dd4e0c7 100644
--- a/substrate/srml/council/src/seats.rs
+++ b/substrate/srml/council/src/seats.rs
@@ -17,7 +17,7 @@
 //! Council system: Handles the voting in and maintenance of council members.
 
 use rstd::prelude::*;
-use primitives::traits::{Zero, One, As, Lookup, OnFinalise};
+use primitives::traits::{Zero, One, As, OnFinalise};
 use runtime_io::print;
 use srml_support::{StorageValue, StorageMap, dispatch::Result};
 use democracy;
diff --git a/substrate/srml/executive/src/lib.rs b/substrate/srml/executive/src/lib.rs
index 19f42888fe..9eb0473a92 100644
--- a/substrate/srml/executive/src/lib.rs
+++ b/substrate/srml/executive/src/lib.rs
@@ -76,23 +76,22 @@ mod internal {
 pub struct Executive<
 	System,
 	Block,
-	Lookup,
+	Context,
 	Payment,
 	Finalisation,
->(PhantomData<(System, Block, Lookup, Payment, Finalisation)>);
+>(PhantomData<(System, Block, Context, Payment, Finalisation)>);
 
 impl<
-	Address,
+	Context: Default,
 	System: system::Trait,
 	Block: traits::Block<Header=System::Header, Hash=System::Hash>,
-	Lookup: traits::Lookup<Source=Address, Target=System::AccountId>,
 	Payment: MakePayment<System::AccountId>,
 	Finalisation: OnFinalise<System::BlockNumber>,
-> Executive<System, Block, Lookup, Payment, Finalisation> where
-	Block::Extrinsic: Checkable<fn(Address) -> Result<System::AccountId, &'static str>> + Codec,
-	<Block::Extrinsic as Checkable<fn(Address) -> Result<System::AccountId, &'static str>>>::Checked: Applyable<Index=System::Index, AccountId=System::AccountId>,
-	<<Block::Extrinsic as Checkable<fn(Address) -> Result<System::AccountId, &'static str>>>::Checked as Applyable>::Call: Dispatchable,
-	<<<Block::Extrinsic as Checkable<fn(Address) -> Result<System::AccountId, &'static str>>>::Checked as Applyable>::Call as Dispatchable>::Origin: From<Option<System::AccountId>>
+> Executive<System, Block, Context, Payment, Finalisation> where
+	Block::Extrinsic: Checkable<Context> + Codec,
+	<Block::Extrinsic as Checkable<Context>>::Checked: Applyable<Index=System::Index, AccountId=System::AccountId>,
+	<<Block::Extrinsic as Checkable<Context>>::Checked as Applyable>::Call: Dispatchable,
+	<<<Block::Extrinsic as Checkable<Context>>::Checked as Applyable>::Call as Dispatchable>::Origin: From<Option<System::AccountId>>
 {
 	/// Start the execution of a particular block.
 	pub fn initialise_block(header: &System::Header) {
@@ -177,13 +176,13 @@ impl<
 	/// Actually apply an extrinsic given its `encoded_len`; this doesn't note its hash.
 	fn apply_extrinsic_no_note_with_len(uxt: Block::Extrinsic, encoded_len: usize) -> result::Result<internal::ApplyOutcome, internal::ApplyError> {
 		// Verify the signature is good.
-		let xt = uxt.check_with(Lookup::lookup).map_err(internal::ApplyError::BadSignature)?;
+		let xt = uxt.check(&Default::default()).map_err(internal::ApplyError::BadSignature)?;
 
-		if let Some(sender) = xt.sender() {
+		if let (Some(sender), Some(index)) = (xt.sender(), xt.index()) {
 			// check index
 			let expected_index = <system::Module<System>>::account_nonce(sender);
-			if xt.index() != &expected_index { return Err(
-				if xt.index() < &expected_index { internal::ApplyError::Stale } else { internal::ApplyError::Future }
+			if index != &expected_index { return Err(
+				if index < &expected_index { internal::ApplyError::Stale } else { internal::ApplyError::Future }
 			) }
 
 			// pay any fees.
@@ -223,7 +222,7 @@ impl<
 	pub fn validate_transaction(uxt: Block::Extrinsic) -> TransactionValidity {
 		let encoded_len = uxt.encode().len();
 		
-		let xt = match uxt.check_with(Lookup::lookup) {
+		let xt = match uxt.check(&Default::default()) {
 			// Checks out. Carry on.
 			Ok(xt) => xt,
 			// An unknown account index implies that the transaction may yet become valid.
@@ -233,7 +232,7 @@ impl<
 			Err(_) => return TransactionValidity::Invalid,
 		};
 
-		if let Some(sender) = xt.sender() {
+		if let (Some(sender), Some(index)) = (xt.sender(), xt.index()) {
 			// pay any fees.
 			if Payment::make_payment(sender, encoded_len).is_err() {
 				return TransactionValidity::Invalid
@@ -241,20 +240,20 @@ impl<
 
 			// check index
 			let mut expected_index = <system::Module<System>>::account_nonce(sender);
-			if xt.index() < &expected_index {
+			if index < &expected_index {
 				return TransactionValidity::Invalid
 			}
-			if *xt.index() > expected_index + As::sa(256) {
+			if *index > expected_index + As::sa(256) {
 				return TransactionValidity::Unknown
 			}
 
 			let mut deps = Vec::new();
-			while expected_index < *xt.index() {
+			while expected_index < *index {
 				deps.push((sender, expected_index).encode());
 				expected_index = expected_index + One::one();
 			}
 			
-			TransactionValidity::Valid(encoded_len as TransactionPriority, deps, vec![(sender, *xt.index()).encode()], TransactionLongevity::max_value())
+			TransactionValidity::Valid(encoded_len as TransactionPriority, deps, vec![(sender, *index).encode()], TransactionLongevity::max_value())
 		} else {
 			return TransactionValidity::Invalid
 		}
@@ -268,19 +267,10 @@ mod tests {
 	use runtime_io::with_externalities;
 	use substrate_primitives::{H256, Blake2Hasher, RlpCodec};
 	use primitives::BuildStorage;
-	use primitives::traits::{Header as HeaderT, BlakeTwo256, Lookup};
+	use primitives::traits::{Header as HeaderT, BlakeTwo256};
 	use primitives::testing::{Digest, DigestItem, Header, Block};
 	use system;
 
-	struct NullLookup;
-	impl Lookup for NullLookup {
-		type Source = u64;
-		type Target = u64;
-		fn lookup(s: Self::Source) -> Result<Self::Target, &'static str> {
-			Ok(s)
-		}
-	}
-
 	impl_outer_origin! {
 		pub enum Origin for Runtime {
 		}
@@ -316,7 +306,7 @@ mod tests {
 	}
 
 	type TestXt = primitives::testing::TestXt<Call<Runtime>>;
-	type Executive = super::Executive<Runtime, Block<TestXt>, NullLookup, balances::Module<Runtime>, ()>;
+	type Executive = super::Executive<Runtime, Block<TestXt>, balances::ChainContext<Runtime>, balances::Module<Runtime>, ()>;
 
 	#[test]
 	fn balance_transfer_dispatch_works() {
diff --git a/substrate/srml/staking/src/lib.rs b/substrate/srml/staking/src/lib.rs
index 50b67332ac..11758e6576 100644
--- a/substrate/srml/staking/src/lib.rs
+++ b/substrate/srml/staking/src/lib.rs
@@ -52,8 +52,7 @@ use rstd::cmp;
 use runtime_support::{Parameter, StorageValue, StorageMap};
 use runtime_support::dispatch::Result;
 use session::OnSessionChange;
-use primitives::traits::{Zero, One, Bounded, OnFinalise,
-	As, Lookup};
+use primitives::traits::{Zero, One, Bounded, OnFinalise, As};
 use balances::{address::Address, OnDilution};
 use system::ensure_signed;
 
diff --git a/substrate/srml/system/src/lib.rs b/substrate/srml/system/src/lib.rs
index cf67f794b0..136bc3ec60 100644
--- a/substrate/srml/system/src/lib.rs
+++ b/substrate/srml/system/src/lib.rs
@@ -44,7 +44,7 @@ extern crate safe_mix;
 
 use rstd::prelude::*;
 use primitives::traits::{self, CheckEqual, SimpleArithmetic, SimpleBitOps, Zero, One, Bounded,
-	Hash, Member, MaybeDisplay, EnsureOrigin, Digest as DigestT, As};
+	Hash, Member, MaybeDisplay, EnsureOrigin, Digest as DigestT, As, GetHeight, BlockNumberToHash};
 use substrate_primitives::storage::well_known_keys;
 use runtime_support::{storage, StorageValue, StorageMap, Parameter};
 use safe_mix::TripletMix;
@@ -384,6 +384,21 @@ impl<T: Trait> Module<T> {
 	}
 }
 
+impl<T: Trait> GetHeight for Module<T> {
+	type BlockNumber = T::BlockNumber;
+	fn get_height(&self) -> Self::BlockNumber {
+		<Module<T>>::block_number()
+	}
+}
+
+impl<T: Trait> BlockNumberToHash for Module<T> {
+	type BlockNumber = T::BlockNumber;
+	type Hash = T::Hash;
+	fn block_number_to_hash(&self, n: Self::BlockNumber) -> Option<Self::Hash> {
+		Some(<Module<T>>::block_hash(n))
+	}
+}
+
 #[cfg(any(feature = "std", test))]
 #[derive(Serialize, Deserialize)]
 #[serde(rename_all = "camelCase")]