[1] Seventy-five six-car trains were built by Metro-Cammell, Washwood Heath, the first entering service on 28 January 1980[2] with last delivered in 1983.

With single-leaf doors and transverse and longitude seating, the style is very similar to 1983 stock on the Jubilee line.

Posters explaining how to operate the doors were put up around Tube stations in English, French and German when the stock was introduced.

[6] It was replaced about 15 years short of its intended lifespan, as a consistent new fleet will allow for frequencies to be increased and will reduce maintenance costs.

It was proposed that the line would be electrified with third rail, similar to the Docklands Light Railway, as opposed to the London Underground or the Southern Region network.

The mid-life refurbishment was the first to be carried out under the public–private partnership (PPP), by Metronet, and was delayed until contract negotiations were completed.

Withdrawals commenced on 19 January 2015 when the first full 6-car train, formed of units 7510 and 7058, was withdrawn from service at Ealing Common Depot and loaded onto trucks for Long Marston for the driving motors to be converted into 230s and the other cars to be either scrapped or stored for future use.

[citation needed] In February 2016, four redundant D78 cars were used by the emergency services in a mock tube accident staged at Littlebrook Power Station.

[citation needed] Car 7027 is preserved at Coopers Lane School, Lewisham for use as a library.

[17] In 2014 Vivarail purchased 156 driving motor cars and 70 trailer vehicles for conversion to diesel–electric multiple units.

[23] The first customer for production Class 230 units was West Midlands Trains, which ordered three two-car DMUs in October 2017.

Subsequently Transport for Wales Rail ordered a total of five three-car sets, to be built as bi-mode multiple units (BMMUs), in June 2018.

[24][25] In September 2019 South Western Railway announced that it would be leasing five two-car Class 484s for use on the upgraded Island Line on the Isle of Wight from 2020.