The British Rail Class 312 alternating current (AC) electric multiple units (EMUs) were built between 1975 and 1978 for use on outer-suburban passenger services. It was the last class of multiple unit to be constructed with the British Rail Mark 2 bodyshell, as well as the last class of multiple unit to be built with slam doors in Britain. These features contributed to their relatively early withdrawal at 25–28 years old, compared with a typical EMU life expectancy of 30–40 years. Description These units were based on the Class 310 used on the suburban services out of London Euston, but were rated for a top speed of , and they had flat windscreens from the outset. The only significant difference between sub-classes was that the 312/1 units were also equipped to work on the 6.25 kV AC overhead electrification system used on parts of the Great Eastern Main Line and London, Tilbury and Southend line networks. British Rail As built, the 312/0 fleet were used on the newly electrified Great Northern outer suburban services from London King's Cross to Royston. The 312/1s were built for Great Eastern line services from London Liverpool Street. The four 312/2 units were mainly used to enhance local services between Birmingham New Street and Birmingham International, but were also used on other services in the West Midlands. During the late 1980s, the class received an interior refurbishment that saw the wooden panel interiors covered with fascia panels, the removal of window blinds and other alterations. At the same time units lost their blue/grey livery (312/0) or all-over blue livery (312/1 and 312/2 as introduced) in favour of Network SouthEast (NSE) livery (312/0-1), whilst of the four 312/2 units, 312204 carried West Midlands Passenger Transport Executive yellow and blue livery and the others were dressed in the standard blue and grey, before their transfer to NSE. At the same time, or soon after, units were reallocated. The Class 312/0 units moved to the Great Eastern Main Line following the arrival of a more modern Class 317 fleet. The 312/1 subfleet consequently moved to the London, Tilbury and Southend line, displacing older Class 302 and 305 units. The section of 6.25 kV on the GEML had been converted to the now standard 25 kV, meaning the exclusive dual-voltage capability of this subfleet would continue to be useful, the line still being dual-voltage at the time. The 312/2