Probably BRs most successful and reliable locomotives the English Electric type 3 or class 37, was the final design descendant of LMS 10000, the first mainline diesel locomotive in the UK. Smaller than the earlier type 4, class 40 locomotives (also produced by Bachmann) and carrying the 12 cylinder version of the same engine set to 1750 bhp. the designers managed to achive significant weight reductions. The four axle plate frame truck of the ponderous class 40 was dispensed with and replaced with smooth riding three axle truck used for the East Coasts' Deltic powered racehorses (class 55 also available from Bachmann). The first batch were sent to the old Great Eastern section where they proved easily capable of handling express passenger services and heavy freight trains. The type quickly spread across the entire BR network, including to the Western region following the policy decision to cease ordering hydraulic type locomotives. The introduction of new type 4 locomotives like the class 47 (Heljan) and 50 (Hornby) displaced the 37s from front line passenger workings to became the principal freight train power across much of the network.
New freight locomotives in the 1980s saw 37s reassigned again. Many were refurbished, some being weighted for heavy freight work, while others were assigned to routes where heavier locomotives were barred. The class always had some passenger train assignments but the addition of electric train heating to some locomotives allowed them to replace older and lower powered locomotives, especially in Scotland and Cornwall.
Until the widespread introduction of EWS class 66 and 67 locomotives the 37 fleet was still almost intact, with only accident casualties withdrawn. Today a core fleet is operational on the national rail network, many working for new owners on freight and tour trains. A number of the class have passed to heritage railways and some are working in continental Europe on hire.