However, it was the success of these tests that contributed to the decision to choose 25 kV AC overhead electrification as standard in Great Britain outside the Southern Region.
The electric service started on 17 August 1953, and the trains, very much seen as experimental, ran until 2 January 1966, when they were withdrawn.
The carriages converted to form the prototype units were drawn from former LNWR electric units built in 1914 by the Metropolitan Carriage, Wagon & Finance Company for use on the West London line fourth-rail DC electrification.
They had been stored early in World War II after the West London route on which they worked was closed to passengers due to bomb damage.
Driving motor coach 28221 was fitted with a germanium rectifier and displayed at the International Railway Congress, Willesden, London between 26 and 29 May 1954.