In the future the trains are planned to operate services on the Reading, Windsor and South West London suburban lines.

[14][15][16][17] In June 2017, SWR awarded a contract to Bombardier Transportation for 90 Aventra DC EMUs, with 60 ten-car and 30 five-car trains to be introduced from mid 2019 at a cost of £895 million.

[4] Following a brief halt to production in March 2020 as a result of the COVID-19 pandemic,[26] the first completed ten-car unit (number 701002) was delivered to Eastleigh Works on 10 June 2020 so that the testing and certification processes could commence.

This caused SWR to extend the lease on its remaining 12 Class 707 units until late 2022, which in turn delayed their planned transfer to Southeastern.

[31] In January 2022, Railway industry journalist Roger Ford observed that the programme met the "ultimate standard for lateness", given that none of the finished units had yet been accepted by SWR and at least 280 vehicles had not yet even been built—while the original contract specified that the entire fleet was to be in service by the end of 2021.

[29] He noted that the delay was, in part, due to "endemic software issues" that had affected the introduction of all Aventra fleets to date.

[29] Other issues include complaints from driver's union ASLEF that the cab environment in the production units differs unacceptably from the standard previously agreed with SWR, and a high level of manufacturing defects in the finished vehicles.

[36] In June 2023 it was reported that 42 finished units had been accepted and that training for depot drivers had begun,[37] and in July it was confirmed that they were planned to be introduced in 2023.

[39] In late December 2023, it was reported that SWR had reached an agreement with the unions allowing for a "Soft Launch" of the Class 701 fleet.