During the late 1950s, British Rail (BR) embarked upon the electrification of the West Coast Main Line, a strategy which necessitated the procurement of a large number of electric locomotives to utilise the newly-installed infrastructure. It was decided that, instead of a bulk order from a single manufacturer, several batches of similar locomotives would be ordered from several companies, the first of these being the AL1 series. Accordingly, it was decided to order the second batch, which was initially classified as the "AL2", to a broadly similar role to the preceding model. Following a review of competitive bids, it was decided to award a contract for ten locomotives to the Metropolitan-Vickers division of the British manufacturing interest Associated Electrical Industries (AEI).