British Rail Class D2/12 was a locomotive commissioned by British Rail in England. It was a diesel powered locomotive in the pre-TOPS period built by Hudswell Clarke with a Gardner engine. The mechanical transmission, using a scoop control fluid coupling and four-speed Power-flow SSS (synchro-self-shifting) gearbox [1], was a Hudswell Clarke speciality.
The D2/12 was mechanically similar to the earlier British Rail Class D2/7 but was of more modern appearance. The engine casing was lower, giving much better all-round visibility.
Ian Allan ABC of British Railways Locomotives, 1966 edition, page 81
Strickland, David C. (1982). Locomotive Directory, every single one there has ever been. Camberley, Surrey: Diesel & Electric Group. p. 41. ISBN0 906375 10 X.