The trains are being supplied under a £895m contract agreed by SWR’s owners First Group and MTR on June 2 2017 and were originally planned to enter service from mid-2019. However, Bombardier told IRJ that it now expects the first trains to enter service in mid-2020.

A completed Aventra EMU at Bombardier's factory in Derby.

The 160km/h trains will be formed into 60 10-car trains and 30 five-car units. Each five-car train will have 274 seats with room for 361 standing passengers, while a 10-car set will seat 556 passengers with space for 746 standing.

SWR will use the trains to increase peak capacity on suburban routes into London Waterloo by 46%. The uniform fleet will replace class 455 EMUs dating from the 1980s as well as the fleet of 30 class 707 Siemens Desiro City five-car EMUs which only entered service in 2017.

The 750V dc third rail Aventra EMUs will be fitted with Britain’s AWS and TPWS national train protection systems as well as ETCS in preparation for Network Rail’s long-term plan for a national roll-out of ETCS announced in June.