Twenty-four British Rail Class 71 (pre-TOPS type HA) were built in 1958 at the British Rail works in Doncaster and in 1964 ten were deemed surplus to requirements, withdrawn from service and placed in storage. The Southern Region was highly impressed with the "little-ED" JA & JB/class 73 locomotives and were keen to see a higher power locomotive with the same flexibility. In 1965, discussions were opened with English Electric (builders of the production JB/Class 73) to produce a high powered electro-diesel. Originally the Waterloo drawing office envisaged a centre-cab design which clearly owed much to the lines of the GE Pennsylvania RailRoad GG1 and dubbed the London Bridge design (page 3 of reference). This was not pursued - possibly due to the historical frugality of the SR and the availability of the ten moth-balled members of Class 71. meant that Crewe Works was chosen for the rebuilds. The redundant HA locomotives were moved in groups to Crewe where they were rebuilt into type HB/Class 74 electro-diesels; the first rebuilt example working under its own power from Crewe to Stewarts Lane depot on 10 November 1967. Buckeye couplers and high-level, or 'bagpipe', control & brake jumpers were fitted to facilitate working with other EP stock - especially TC units in push-pull mode. Also, two-tone "raspberry" air horns were mounted on the cab roof, replacing the original air whistle of Class 71 locomotives.