The class 35 was a single-engine, medium diesel-hydraulic locomotive designed for mixed traffic in the Western Region. While the locomotive itself was a British design and not derived from a German one like the classes 42 and 43 “Warship”, it used a German power train. The engine was a 1,700 hp Maybach MD870 built under license by Bristol-Siddeley. The hydro-mechanical Mekydro gearbox was built by Stone-Platt Industries. Assembly of the locomotives took place at Beyer, Peacock, which founded the Beyer Peacock (Hymek) Ltd. for this purpose.

101 locomotives were built between 1961 and 1964 and numbered D7000 to D7100. They quickly got the nickname “Hymeks”. They were used in all kinds of services and often had to haul heavier trains than they were designed for, what led to increased wear. Sometimes they even had to take over express services from the King class. Their withdrawals already took place between 1971 and 1975 after all diesel-hydraulic classes had been classified as non-standard. Additionally, they had only steam train heating, while newer passenger carriages had to be heated and air-conditioned electrically. Of four class 35 locomotives which have been preserved, two are currently operational.