British Rail reserved the TOPS Class 97 designation for departmental locomotives, which were used for special or engineering duties. They were therefore of several different classes, lumped together for numbering purposes. Some locomotives were converted from redundant engines, whilst others were purpose built. In 2008, Network Rail once again used Class 97 for signalling test locomotives (Class 97/3). Allocation of numbers Class 97 numbers were allocated in one of three ways: Application of 97 prefix to pre-TOPS number – e.g. Western Region shunters PWM 650–654 became 97650–97654. TOPS class number replaced by 97 prefix – e.g. Former Class 47 locomotive 47472 became 97472. Allocation of number in a series commencing from 97x01, where x represented the engine power Type (1 to 5), '7' for ex-multiple unit conversions and '8' for diesel shunters. Locomotive descriptions 97020 Built by Ruston & Hornsby in January 1957 with the serial number 408493, this 4wDM shunter was ordered specifically for departmental use by the Signalling & Telecommunications department of the Western region at Reading Signal Works. The transmission was diesel mechanical, although the wheels were chain driven from the gearbox and the loco was rated at for a weight of only 17 tons. Tractive effort was a maximum of . Delivered to the WR with the number 20 it was renumbered to 97020 in May 1980. However withdrawal came in April 1981 and it was scrapped on site in August 1982 by Cartwrights of Tipton. For refuelling, it had to go via the main line to the depot at Reading. 97201 This locomotive was a former Class 24 locomotive No.24061, which was taken over by the Railway Technical Centre, based at Derby, in 1975. It was initially numbered RDB 968007, and was given its Class 97 number in 1979. It was employed hauling various test-trains until retirement in 1988. It was painted in RTC's distinctive red/blue livery, and named "Experiment". After withdrawal it was preserved on the Midland Railway Centre having been to Vic Berrys at Leicester for Asbestos Removal then later the East Lancs Railway before a spell at the North Tyneside Steam Railway before later moving to the North Yorkshire Moors Railway. 97202 This was former Class 25 locomotive 25131 used for training purposes at Toton depot. It had been withdrawn on 6 December 1982 and was reinstated as 97202 on 1 October 1983. It only lasted in Departmental service until January 1984