They were built in the late 1980s and early 1990s by British Rail Engineering Limited (which became part of ABB in September 1992) and Metro Cammell.

[1] Unlike previous contemporary rolling stock units in Britain, Networker trains would use aluminium bodies to save weight.

The design was to cover all requirements for future NSE multiple units, including new routes such as the Channel Tunnel Rail Link.

[1] However, due to the recession in the early 1990s and the privatisation of British Rail from 1994, around 340 trains were built, substantially fewer than originally planned.

[1] These designations applied to a single four-car electric multiple unit (EMU), converted from former Class 210 carriages, that was used as a research prototype.

[3] Forty-one 4-car units were built from 1994 to 1995,[4] the first sixteen fitted with pick-up shoes for power from 750 V DC third rail on services between London and Kent,[5] and the other twenty-five fitted with pantographs for power from 25 kV AC overhead line equipment on services on the East Coast Main Line from London King's Cross to Peterborough and King's Lynn.

300 Class 331 'Networker LT&S' carriages were planned, as part of a 'Total Route Modernisation' of the London, Tilbury and Southend line.

Classes 371 and 381 were proposed as the "Universal Networker", a dual voltage train type for a multitude of services including Kent Coast, Great Northern, Thameslink and LTS routes.

Class 471 was the proposed "main line Networker" intended for long-distance services from London to Kent and Sussex.