In 1937 Robert Stephenson & Co. Ltd purchased the locomotive department of R & W Hawthorn Leslie & Co. Ltd. They became Robert Stephenson and Hawthorns Ltd. The policy was to concentrate the building of main line locomotives at Robert Stephenson’s Darlington works and industrial locomotives at Forth Banks. In 1944 Vulcan Foundry acquired Robert Stephenson and Hawthorns Ltd, ending Hawthorns' 137 year connection with Forth Banks. In 1955 Vulcan Foundry became full members of the English Electric group of companies, which became part of the GEC group of companies in 1968.

In 1883 Dick Kerr & Co Ltd was formed with John Kerr to take on the railway and tramway related activities built up by W B Dick & Co Ltd in Kilmarnock (Britannia Works). The company built steam locomotives to haul tramcars; and in 1887 constructed the first section of the cable tramway system in Edinburgh. In 1897, Dick, Kerr acquired disused premises, later known as East Works, in Preston for the manufacture of electric tramcars and rolling stock under the control of a subsidiary company, the Electric Railway and Tramway Carriage Works Limited (ER&TCW), later known as the United Electric Car Company Limited. The works developed a world market for electric urban tramway systems; however drive machinery for the vehicles had to be imported from the USA. The company provided complete electric coaches for the Waterloo & City Railway in 1899, and in 1904 equipped the first main line in Great Britain to be electrified between Liverpool and Southport. In 1900, the new works known as West Works were built by the English Electric Manufacturing company on the opposite side of Strand Road to the ER&TCW works, the rear boundary of the site being along the line of the original bank of the river Ribble. The factory was built for the manufacture of electric traction equipments, power station equipments and general engineering. In 1902, these works at Preston were taken over by Dick, Kerr & Co Limited. In 1917 the company acquired Preston based tram maker United Electric Car Company creating Britain's largest tram factory, and also a controlling interest in Willans and Robinson, Rugby. In 1918, Dick, Kerr and Co Ltd became one of the founding companies of the English Electric Co Ltd.

The English Electric Company was formed on 14th December 1918 and over the following year acquired Dick, Kerr & Company of Preston, Willans & Robinson of Rugby, the Phoenix Dynamo Manufacturing Company of Bradford, and Coventry Ordnance Works. After the First World War the various German owned Siemens works were distributed to different UK companies and in November 1919 English Electric acquired the Siemens Brothers Dynamo Works at Stafford, which became the company headquarters in 1931. Coventry Ordnance, primary output naval guns, did not feature in the gradual product rationalisation which took place between the First World and Second world Wars. Willans & Robinson’s Rugby works specialised in prime movers, steam, hydro and internal combustion, and their Stafford works on power station and distribution electrics, including transformers and large electric machines for applications such as mining and steel works. Dick Kerr & Company continued building equipment and vehicles for bus, tram and railway applications with the Phoenix Dynamo Manufacturing Company concentrating on medium and small electrical machines. Involvement with aircraft continued a small scale. By 1929 the company was in financial trouble and an American syndicate fronted by Lazard Bros. put in new capital. In 1930 Westinghouse of Pittsburgh entered into an agreement with the company for the exchange of technical information relating to steam turbines and electrical apparatus. This cooperation continued into the 1950s. 1930 saw the closure of Preston West works and the transfer of traction electrical design and manufacture to the Phoenix Dynamo Manufacturing works. The Westinghouse influence included top management changes with Sir H Mensforth becoming chairman and George Nelson managing director. Both had been with British Westinghouse at Trafford Park. The early 1930s saw a remarkable improvement in the company’s finances and domestic appliance manufacture was started at Bradford and Stafford. In 1936 they began production of diesel locomotives at Preston and were later involved in the production of the Deltic locomotive for British Rail, presaging the end of steam traction in the UK. Extensive shadow factory building for war production commenced in the late 1930’s, including at Preston East works and Salmesbury for aircraft production and at East Lancashire Road, Liverpool for D. Napier aero engines. A large variety of military equipment built during the war included thousands of Cromwell tanks from Stafford and over 3000 Handley Page Hampden and Halifax bombers from Preston and Salmesbury. After the war manufacture of smaller products from Bradford and Stafford moved to the large Liverpool works. This included electrical distribution transformers, switchgear, fuse gear, fractional horsepower motors and domestic appliances. Napier’s continued engine manufacture with the development of the ’Deltic’ diesel engine, mainly for marine applications. The nearby Netherton works took over the manufacture of large hydro-electric turbines and generators from Willans and Stafford. In 1942 English Electric acquired D. Napier & Son Ltd and Marconi in 1946. The company went on to extend their railway interests with the acquisition of the Vulcan Foundry and Robert Stephenson and Hawthorn Ltd in 1955. The company tried to take over The General Electric Company (GEC) in 1960 but failed. Traction manufacture, but not the offices, moved back to Preston East works and ‘K’, ‘RK’ and ‘V’ engine design and manufacture moved from Willans to Preston West works which was now also used for locomotive building. Kidsgrove works in Stafford made industrial controls and for a while was a major player in the UK computer industry, merging with Leo Computers and then into ICL. Train performance calculations were an early user of the mid-fifties ‘Deuce’ computer. Preston also became a major player in the aircraft industry taking over the wartime RAF/USAF base at Warton aerodrome - major design and manufacture contracts included Canberra bombers and Lightning fighters. Rationalisation in the 1960s resulted in English Electric Aviation becoming 40% of the new British Aircraft Corporation. In 1961 English Electric took over Dorman Diesels Ltd which in turn had acquired W. G. Bagnall Ltd. In 1966 English Electric Diesels merged with Ruston and Hornsby which already included Paxmans. This company eventually became GEC Diesels. Elliott Automation was acquired in 1967. The following year GEC took over English Electric, ending its independent existence.

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.