Metropolitan-Vickers Electrical Co Ltd was the new trading name given to British Westinghouse Electric and Manufacturing Co on 8 September 1919. The predecessor company had sold its controlling share to the Metropolitan Carriage Wagon Co in 1916 in order to gain membership of the Federation of British Industries. In 1919, Vickers acquired the Metropolitan Carriage Wagon Co, along with its controlling share in British Westinghouse, prompting the change in name to Metropolitan-Vickers Electrical Co Ltd. The American owned British Westinghouse had established its English operations at Trafford Park in 1899, and Metropolitan-Vickers Electrical Co Ltd continued on the same site from 8 September 1919. The company was initially known for its electricity generators, later diversifying into the manufacture of steam turbines, switchgear, transformers, electronics and railway traction equipment. The passing of the Electricity (Supply) Act in 1926 provided a boost to the company’s post-war fortunes, with the creation of the National Grid generating demand for the company's products. In 1928, Metropolitan-Vickers Electrical Co Ltd merged with its rival British Thomson Houston Co Ltd, retaining both names for trading purposes. The following year, on 4 January 1929, Associated Electrical Industries Ltd (AEI) acquired Metropolitan-Vickers Electrical Co Ltd and the British Thomson Houston Co Ltd. Again, both trading names were retained, and a fierce rivalry was established between the firms which the parent company was unable to control. In 1931, Sir Felix Pole joined Metropolitan-Vickers Electrical Co Ltd as its new chairman. He oversaw a period of expansion for the company leading into the Second World War. In 1939, seeking a more concise name for the company, the Board of Directors decided upon Metrovicks, which became interchangeable with the official company name of Metropolitan-Vickers Electrical Co Ltd. Under Sir Felix Pole's chairmanship, Metropolitan-Vickers developed new products for the aviation industry and during the war was one of the sites where Lancaster bombers were built. In 1941, the company developed the first British axial-flow jet engine, the Metrovick F.2. Following the Second World War, the company appointed Oliver Lyttelton as chairman, with the aim of increasing the efficiency and productivity of AEI. Despite his success in achieving this aim, Lyttelton was unable to resolve the commercial rivalry between Metropolitan-Vickers Electrical Co Ltd and the British Thomson Houston Co Ltd. During his second period as chairman, from 1954-1963, Lyttelton, now Lord Chandos, oversaw the development by Metropolitan-Vickers Electrical Co Ltd of the first commercial transistor computer, the Metrovick 950. Chandos also resolved to extinguish the competition and internal divisions between Metropolitan-Vickers Electrical Co Ltd and the British Thomson Houston Co Ltd, and both company names ceased to be used from 1 January 1960, with all subsidiaries going on to trade under the name of Associated Electrical Industries Ltd.

The Ruston-Paxman Group was formed following the merger of Ruston and Hornsby with Davey, Paxman and Co Ltd in 1940. The constituent companies continued to trade under their original names, manufacturing traction and stationary engines. The company entered the rail traction market in the 1930’s and in 1950 they teamed up with British Thomson-Houston and the North British Locomotive Company to produce what became a ‘Type 1’ loco using their 16RPHXL engine, these engines were used in some other early British Rail prototypes. These, what were then relatively high speed (1500 rpm) engines, were not as reliable as the medium speed types and were not used in large numbers in the 1955 modernisation plan. A number of locomotives using two smaller engines were supplied to New South Wales and Western Australia railways. By 1961, the Group manufactured gas, oil, diesel and marine engines, gas turbines, diesel locomotives, boilers, steel tanks and vessels, pumps and pumping plants, rotary industrial filters and chemical plant, employing 10,590 people. The Group was acquired by English Electric in 1966, with their diesel interests becoming part of English Electric Diesels Ltd in 1968. After incorporation into English Electric and then GEC the much more powerful 1500 rpm Valenta engines which had been developed in the meantime, mainly for marine applications, were incorporated in the British Rail ‘High Speed Train’. These were very successful and were produced in sufficient numbers to cover most of British Rail’s ’Intercity’ non electrified services. Similar trains were supplied to Australia. After over 20 years of intensive service the HST’s have been refurbished, some with Paxman VP185 engines, but most with an MTU engine. After the GEC - Alsthom merger, all the surviving diesel operations including Paxmans and Mirlees Blackstone which had been taken over in 1997 became Alstom Engines Ltd. In 1998 the company was sold to MAN B&W in 2000.

The General Electric Company (GEC) merged AEI Traction Division and English Electric Traction in 1969 after acquiring both companies to create English Electric – AEI Traction Limited. The headquarters were located at Trafford Park in Manchester. This subsidiary company was renamed GEC Traction Limited in 1972.

GEC Traction (GECT) was formed in 1972 as part of the GEC Power Engineering Group following earlier amalgamations of the traction divisions of the General Electric Company (GEC), the English Electric Company (EE) and Associated Electrical Industries (AEI). A wholly owned subsidiary company of GEC, the company had offices and works, located at Trafford Park in Manchester, at Strand Road in Preston, and at Attercliffe Common, Sheffield. The headquarters of GEC Traction was Trafford Park, Manchester (previously the headquarters of English Electric-AEI Traction) with design of rotating machines at Preston and Sheffield, and manufacturing activities for control equipment at Manchester and Preston. GEC Traction designed and manufactured a full range of traction machines and control equipment for electric vehicles, including electric locomotives and multiple unit trains for main-line and mass-transit railway systems (dc up to 3,000 volts, and ac up to 50,000 volts), diesel-electric locomotives and trains, mining and industrial locomotives, tramcars and trolleybuses. GEC Traction was the leading supplier of traction equipment in the UK and had a wide market around the world, particularly in South Africa, Australasia, Hong Kong, South Korea, South America and Pakistan. In 1979 the Industrial Locomotive Division of the former English Electric which was based at Vulcan Works, Newton-le-Willows was merged into GEC Traction, which later became a separate company, GEC Industrial Locomotives Ltd. During the late 1980s and 1990s the firm underwent major rationalisation, involving closure of several sites including Attercliffe Common in Sheffield in 1985 and the company’s headquarters at Trafford Park in Manchester in 1998. The company name GEC Traction endured until a merger with the French Alsthom group in 1989, which created GEC Alsthom Traction, which was still a branch of the main company GEC Alsthom.