The early 1950s were a time of great plans and modern ideas, not least where the railways were concerned, but still recovering from the financial effects of the Second World War, many of these plans had to be implemented in a measured way. Electric traction was seen by the newly nationalised British Rail to be the answer and so attention was focused on new routes in the Southern Region, where third rail electrification had been in place since 1923. Much of BR’s Southern Region passenger traffic could be accommodated by the use of EMUs, but to cover the motive power requirement for 900 ton freight services, as well as the "Night Ferry" and "Golden Arrow" workings, a new electric locomotive was required.

The design specification was based on the experience gained in the previous fifteen years, through the operation of Bulleid’s CC1 & CC2, Class 70 locomotives. By adopting the continental practice of reducing the weight, without sacrificing tractive effort, a smaller engine could be built, resulting in a 750v DC, 77 ton, Bo-Bo locomotive, 24 of which were built by BR’s Doncaster works between 1958 and 1960. Numbered E5000 – E5023 as built (E5000 was subsequently renumbered to E5024 in December 1962), the type was classified by BR Southern Region as HA. To enable operation under the simple catenary wires erected in a number of Kentish yards at that time, a single pantograph was fitted centrally on the roof and a booster system was also fitted, avoiding the problem of ‘gapping’ across short breaks in the conductor rail.

Ten of the class were converted to Class 74 engines in 1967/68, at a time when passenger duties for the Class 71s were being reduced and despite being moved onto extra freight workings, the type was under-utilised. In 1977, it was decided that the Class 33 and 73 Electro-diesels could take over the Class 71’s duties and they were withdrawn from service.

Locomotive E5022 was re-numbered as E5006 in September 1968, to take up the gap in numbering caused by the withdrawal of locomotives for conversion to Class 74. Under the TOPS renumbering system, the locomotive took on the number 71006 and was finally withdrawn in November 1977, being scrapped at Cashmore’s in Newport during August 1978.