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 British Thomson-Houston Co. Ltd., (BTH) was created as a subsidiary of the General Electric Company, USA in 1896 to exploit the sale of products in the United Kingdom. BTH was a reconstruction of an existing firm, Laing, Wharton and Down (1886). The BTH manufacturing works were based at Rugby, Warwickshire and the company’s products included induction motors, alternators, switchgear, turbo-generators and turbines, as well as a large number of rotary converters and motor converters, primarily for chemical plants. During the First World War, BTH’s most significant contribution was the development of marine apparatus for the naval service. The 1920s saw a period of vast expansion for the company with new extensions built at many of its factories such as Willesden, Birmingham, Chesterfield and Lutterworth. BTH amalgamated with Metropolitan-Vickers Electrical Company Ltd to form Associated Electrical Industries (AEI) in 1928 although both companies retained their separate identities and continued to compete for the same contracts. BTH developed manufactured electric torpedoes and electrical components for aircraft engines, munitions, etc., during the Second World War and in 1935 independently of each other, BTH and Metropolitan-Vickers were the first two companies in the world to construct jet engines.

Associated Electrical Industries (AEI) was formed in 1928 as a financial holding company for a number of leading electrical manufacturing and trading companies in the United Kingdom. The two major constituent companies were British Thomson-Houston (BTH) based at Rugby, (Mill Road Works) and Metropolitan-Vickers Electrical Company Ltd (Metrovicks) situated at Trafford Park, Manchester. However, fierce rivalry existed between the Metrovick and BTH brands resulting in internal competition and duplicated management. This was highlighted during the Second World War in 1939, when Metrovicks and BTH became the first two firms in the world to construct jet engines (independently from each other). Following the Second World War, in 1954, AEI expanded to consist of BTH, Metrovicks, Edison Swan Electric Co, Ferguson Pailin, Hotpoint Electric Appliance Co, International Refrigerator Co, Newton Victor, Sunvic Controls, Premier Electric Heaters, Siemens Bros (1955) and Birlec (1954). In 1959 AEI decided to remove the familiar brands of BTH and Metrovicks and consolidate both as AEI resulting in internal problems and a fall in sales and market value. However, AEI acquired a variety of companies from 1959 to 1967, these included Associated Insulation Products, W. T. Henley’s Telegraph Works Co (1958), and London Electric Wire Co and Smiths (1958), Submarine Cables, Hackbridge Holdings Ltd., The Lancashire Dynamo and Crypto Ltd., W.T. Avery Ltd., Henley and Schreiber. The General Electric Company bought AEI in 1967.

The General Electric Company (GEC) was created as the General Electric Apparatus Company in 1886 by Hugo Hirst and Gustav Byng from a small electrical business established in London by Byng (Gustav Binswanger and Company, using Byng's original name). In 1887 GEC published the first electrical catalogue of its kind. The following year the company acquired its first factory in Manchester where telephones, electric bells, ceiling roses and switches were manufactured. In 1889, the General Electric Co. Ltd. was formed as a private limited company and moved to larger premises at 71, Queen Victoria Street. Now known also as G.E.C., the company was expanding rapidly, opening new branches and factories. Initially manufacture was focussed on electric bells and light fittings, but this expanded to a wide range of electrical equipment - resulting in the firm's slogan 'Everything Electrical'. In 1893, GEC decided to invest in lamp manufacture. The resulting company, (to become Osram in 1909), was to lead the way in lamp design and the burgeoning demand for electric lighting was to make GEC's fortune. In 1900, GEC was incorporated as a public limited company, The General Electric Company (1900) Ltd, (the '1900' was dropped three years later). In 1902, GEC's first purpose-built factory, the Witton Engineering Works was opened near Birmingham which designed and manufactured electrical equipment and machines. Rapidly growing private and commercial use of electricity ensured buoyant demand and the company expanded both at home and overseas, with the establishment of agencies in Europe, Japan, Australia, South Africa and India and a substantial export trade to South America. The outbreak of the First World War transformed GEC into a major player in the electrical industry with profits to match. The company was heavily involved in the war effort, with products such as radios, signalling lamps and arc-lamp carbons. Between the wars, GEC expanded to become an international corporation and a national institution. The take-over of Fraser and Chalmers in 1918 took GEC into heavy engineering and consolidated their claim to supply 'Everything Electrical'. Other major factories included Osram Lamps at Hammersmith and the telephone works in Coventry. During the 1920s, the company was heavily involved in the creation of the UK national grid. In addition, the opening of the new purpose built company headquarters in Kingsway, London in 1921, and the pioneering industrial research laboratories at Wembley in 1923, were symbolic of the continuing expansion of both GEC and the electrical industry. The company took over several companies in the Birmingham area and elsewhere. After being a minor player in tram equipment, the company entered the heavy rail electric traction market in the 1920’s and 30’s. During the Second World War, GEC was a major supplier to the military of electrical and engineering products. Significant contributions to the war effort included the development of the cavity magnetron for radar, advances in communications technology and the on-going mass production of lamps and lighting equipment. After the war the company continued in the full range of electrical equipment from electronics to atomic power stations, but was not very profitable. In 1961, after a failed takeover bid from the English Electric Company, GEC took over Radio and Allied Industries, a small but very profitable television set manufacturer. Michael Sobell and Arnold Weinstock from this company became GEC directors with a substantial shareholding. Weinstock became managing director in 1963 and undertook drastic changes to make the company more profitable. The rail traction operations were closed and the heavy electrical/ power station businesses were sold to Parsons. A number of ex GEC employees were recruited by Associated Electrical Industries (AEI). A hostile takeover bid was made for AEI in 1967 and the relative profitability/share prices enabled GEC to take over the much larger AEI. In 1968 English Electric agreed to merge with GEC. Further takeovers and mergers made the company one of the largest private employers in the UK. In 1989, Arnold Weinstock agreed a merger between the power and transport businesses of GEC and those of Alsthom of France, part of Compagnie Générale d’Electricité (CGE) to form GEC Alsthom. While Weinstock was in charge the UK arm, the company continued to prosper, but after his death of his son in 1996 he was asked to retire and most of the company’s operations were transferred to France, or were sold off. Small sales and service operations remain for some of the products. Many of the factories have been demolished, with only Stafford continuing on a moderate scale.