D7001 at Cranmore in July 1973. © Gordon Edgar
The Class 35s (aka "Hymeks") were a mixed-traffic diesel-hydraulic class of locomotives built in the early 1960s. They were developed for the Western Region of British Railways, which had opted for lightweight hydraulic locomotives following the BR modernisation plan of 1955. The class initially worked on secondary passenger services out of Bristol and proved so successful that they were promoted to express workings between Paddington and Swansea, displacing the King class steam locomotives. The class also saw work on numerous freight workings in the region and were famously used as banking locomotives on the Lickey incline. Due to their non-standard hydraulic transmission, the Hymeks faced early withdrawal and were taken out of serivce by 1975.
(Information provided by Wikipedia)