This class of five locomotives is outwardly similar to the Class 04 locomotives built around the same time but, internally, they are quite different. The Class 97/6 is diesel-electric while the Class 04 is diesel-mechanical.
The fleet was originally numbered PWM650-654 in the Western Region Permanent Way Machines series, but were renumbered into the Class 97 series between 1979-1981. Locomotives were original painted in BR Green livery, which was later superseded by BR Blue and finally Civil Engineering Yellow liveries. They were employed at various locations, including Reading West (97650/653/654), Gloucester / Cardiff Canton / Radyr (97651) and Plymouth Laira (97652).
With the privatisation of British Rail these locomotives were largely made redundant. Three locomotives had already been withdrawn from traffic, and only nos. 97651 and 97654 survived long enough to pass into English Welsh & Scottish (EWS) ownership. Number 97654 was sold to an infrastructure company based in Edinburgh, and remained in use until 2005, when it was preserved. Number 97651 was one of the first locomotives sold by EWS into preservation.