BR/AEI & English Electric

'BR/AEI & English Electric' is used in this encyclopedia for the design partnerships between British Railways, Associated Electrical Industries (AEI — the parent company of Metropolitan-Vickers and British Thomson-Houston), and English Electric, for several of the AC electric locomotive classes ordered for the West Coast Main Line electrification of 1959–1974. The first phase of WCML electrification, energised between Styal and Manchester in 1959 and extended progressively south to Euston by 1966, required a fleet of capable 25 kV 50 Hz AC electric locomotives, and BR adopted a pilot-scheme approach in which five different manufacturers each supplied a small batch of locomotives to a common BR performance specification.

AEI supplied the electrical equipment for the Class 81 (AL1) locomotives built by Birmingham Railway Carriage and Wagon Company, and for the Class 82 (AL2) built by Beyer Peacock — both using AEI traction motors and control gear. English Electric supplied electrical equipment for the Class 83 (AL3) built by English Electric's own Vulcan Foundry. The collaborative arrangement reflected the structure of British electrical manufacturing in the early 1960s, where locomotive builders and electrical equipment suppliers operated as distinct entities that had to be brought together for each project through a prime contractor arrangement.

The pilot-scheme philosophy allowed BR to evaluate different design approaches across the five AL classes before standardising on the Class 86 (AL6) for the production fleet, which used AEI electrical equipment and represented the mature development of WCML electric locomotive design. The Class 87 and Class 90 that followed built on this foundation, giving the WCML a family of AC electric locomotives capable of the sustained 100 mph performance that the electrified main line demanded.