A popular and versatile 56-year-old British Rail Bo-Bo diesel locomotive is to join the roster for the Gloucestershire Warwickshire Railway's annual Summer Heritage Diesel Gala from July 7-9.

The locomotive in question is recently restored Sulzer Type 2 / British Rail Class 25 No. D7659 (7659/25309/25909), and is appearing courtesy of Peak Rail and the Waterman Railway Heritage Trust.

327 locomotives were built between 1961 and 1967, with construction being carried out at British Railways' Crewe Works, Darlington Works, Derby Works, and by Beyer Peacock & Co in Manchester.

Numbered in two series between D5151-D5299 and D7500-D7677, the Type 2s were fitted with 1,250 bhp Sulzer 6LDA28-B engines and primarily operated freight services from the outset.

However, they could also be found taking charge of passenger trains with a number of the class being fitted with boilers to provide steam heating for such services. With a route availability of 5 (RA5), the Sulzer Type 2s could be found pretty much anywhere across the British Rail network, which quickly brought about the nickname 'Rats' amongst rail enthusiasts.

Regular performers throughout the 1970s and the early 1980s, they were also known for operating summer Saturday trains to Aberystwyth and workings between Crewe and Cardiff. Members of the class were progressively withdrawn during the 1980s with the final example being taken out of service in March 1987 - this being No. D7672/25322. This particular '25' was subsequently restored and continued to operate until 1991 working on various railtours. Of the 327 locomotives built, 20 survived into preservation and are either in storage, operational or undergoing restoration.

On the 11th December 1985, 25309 was once again renumbered, this time to 25909, in readiness for operating freight traffic for BR Railfreight's Industrial Materials Division. However, this traffic sadly never materialised and 25909 went into storage as unserviceable on the 11th August 1986. A month later, the locomotive was officially withdrawn and became the 284th member of the class to be retired from British Rail service.

Tickets for the summer diesel gala are available via the GWSR website. With up to eight diesel locomotives and a diesel multiple unit (DMU) running, it will offer an action-packed timetable of trains.

The locomotive and carriage and wagon workshops will throw open their doors for rare behind-the-scenes visits and there will be plenty of other activity at the railway's picturesque period stations.