The contract is worth £73m and includes an expansion to the existing train service agreement. The new trains will boost capacity through the central section of the line which will use the new Crossrail tunnels as well as services to Reading and London Heathrow Airport Terminal 5.

Each train will be able to carry up to 1500 passengers, and will feature air-conditioning, open gangways, and will incorporate the latest onboard energy management systems. In addition, the trains will utilise the latest condition-based maintenance systems, including the Bombardier Orbita predictive maintenance platform and an automated vehicle inspection system.

The additional cars will be added to the 585 already in production in Derby for the new east-west line with 15 seven-car class 345s now in service for TfL Rail between London Liverpool Street and Shenfield. Driver training with the new sets is also taking place on the Great Western Main Line from the Old Oak Common depot while testing is underway through the central tunnel and on the Heathrow Airport branch.

Services will commence between London Paddington and Abbey Wood, Heathrow - Paddington, and London Liverpool Street - Shenfield in December ahead of the complete west-east service from Heathrow and Reading to Abbey Wood and Shenfield in December 2019. The new line is expected to serve 200 million passengers per year and add 10% to central London’s rail capacity.