D7612 is a Sulzer Type 2 locomotive (later Class 25) and was built at British Railways’ Derby works and first allocated to Glasgow Eastfield in April 1966.

 It was one of thirteen allocated to the Scottish Region fitted with single line token catcher recesses in the cab sides under the driver’s windows, however moved south within a year, moving to Derby in September 1967, then Nottingham and Birmingham until allocated to Bescot in 1973. It worked from Bescot until being placed into store (unserviceable) in April 1982 at Derby with power unit problems. It received the power unit from 25 274 and was restored to service at Bescot in May 1982.

25 262, as it had become by then, went back north in 1985 and was allocated to Carlisle Kingmoor. It was renumbered 25 901 in December 1985 as part of a sub class of twelve locos for use on the industrial minerals and chemical sectors of BR. All of the Class 25s were withdrawn in 1987 with 25 901 being officially withdrawn on 16th March 1987. However the loco worked on past this date on trip work and is thought to be the last Class 25 to work a normal BR service towards the end of April 1987.

It was purchased by the Harry Needle Railroad Company and, in September 1989, moved to the East Lancashire Railway. It was later sold on to a small group of members on that railway and sold on again to South Devon Diesel Traction in 1999 and moved to the South Devon Railway.