The bulk of the air-conditioned trains will be for operation on the lines from London Liverpool Street to Endfield Town, Cheshunt and Chingford, plus the Romford – Upminster shuttle, which became part of the London Overground network in May. Here 31 four-car trains will be introduced to replace existing class 315 and 317 EMUs.

Eight four-car EMUs will be supplied for the Gospel Oak – Barking line which is being electrified, replacing the class 172 DMUs currently operating on the route.

Finally, the contract will include six additional four-car EMUs to increase capacity on the existing Overground network.

TfL shortlisted Bombardier, CAF, Hitachi Rail Europe and Siemens for the contract in July 2014.