In January 1958, following on from the policy established by the Modernisation Plan of 1955, the first of the Western Region's new diesel-hydraulic class was delivered. A press run was arranged for 17th February 1958, when D600 hauled a 340 ton train between London Paddington and Bristol Temple Meads with stops at Reading, Didcot and Swindon. The twin engine reliability came in handy when one of the engines cut out soon after leaving Bristol on the return run; the last 100 miles back to London were on one engine only. D600 was the first of a pilot scheme of A1A-A1a locomotives that were then followed by a further batch of 71 B-B locomotives delivered between July 1958 and June 1962.Designed to replace steam on the WR's express services, there were the inevitable teething problems with the new technology and, for many who grew up with steam, there was a particular delight in seeing the errant hydraulics being rescued by the steam locomotives that the diesels had been bought to replace. With the locomotives named after, with two exceptions, ships of the Royal Navy, it was inevitable that the class became nicknamed the 'Warships'. The pilot scheme quintet proved to have relatively short lives, being withdrawn in 1967 (although one languished at Barry until June 1980) and the remainder of the type were withdrawn, as increasingly non-standard, between August 1968 and December 1972. Two of the type survive in preservation. Fully illustrated, this is a fascinating addition to the respected "Heyday" series and will provide useful additional information on one of the first diesel hydraulic locomotives to enter service on the Western Region.