BR Southern Region / English Electric

'BR Southern Region / English Electric' is used in this encyclopedia where a Southern Region traction project was designed as a collaboration between the Southern Region engineering office and English Electric, the major British electrical engineering and locomotive manufacturing firm whose Vulcan Foundry at Newton-le-Willows and electrical works at Bradford and Preston gave it the manufacturing capability to partner with the SR on electric and electro-diesel locomotive projects.

English Electric was one of the dominant names in British railway traction in the post-war era, supplying diesel and electric power equipment for numerous BR classes and holding a strong position in the market for both diesel locomotives and electric traction systems. The firm's expertise in electric traction systems made it a natural partner for the Southern Region, whose third-rail 750 V DC network required specialist electrical engineering for its locomotive fleet.

The collaboration produced principally the Class 71 Bo-Bo electric locomotive, designed for the demanding requirements of heavy express and freight workings on the SR's electrified main lines, and contributed to the Class 73 electro-diesel through the supply of English Electric's diesel engine and electrical equipment. The English Electric 6K diesel engine in the Class 73 gave the electro-diesel adequate performance for its secondary-line and cross-boundary duties, while EE's electrical engineering ensured efficient operation from the third rail at higher power ratings. This partnership embodied the pragmatic approach that characterised the best of BR's collaborative diesel and electric procurement.