Class 121 Pressed Steel Single / 2-car DMUs

Introduced: 1960
Coupling code: Blue Square
Underframe: 64ft 6in
Engines: AEC 150hp
Transmission: Mechanical

Following the success of the Gloucester Singles the Western Region ordered a further batch of sixteen single cars and ten trailers, this time built by Pressed Steel in Linwood (Scotland).

The units took over services originally monopolised by GWR built railcars but as more and more cross country and branch lines closed that work became less and less. Consequently, the class was concentrated around the Reading, Bristol, Cardiff and Plymouth areas. They were used on the West London branch lines, the Severn Beach branch, lines in the Welsh valleys and the Cornish branch lines.

They are one of only three classes to have passenger vehicles that were formally named (the others being a 115 and 117s).

They were very popular for departmental use and preservation. Some vehicles returned to passenger traffic for Chiltern Railways and Arriva Trains Wales - they remained the last type of first generation DMU in mainline passenger use finally succumming in 2017.