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.

The Vulcan Foundry was originally opened in 1830 at Newton-le-Willows, as Charles Tayleur and Company. It initially produced girders for bridges, switches and crossings, and other ironwork following the opening of the Liverpool and Manchester Railway. Robert Stephenson became a partner in 1832, and in the same year, the first locomotives ‘Tayleur’ and ‘Stephenson’ were delivered to the North Union Railway. By 1840 locomotives had been delivered to five European countries and to North America. The company became The Vulcan Foundry Company in 1847 and acquired limited liability in 1864. From the beginning of 1898, the name changed again to The Vulcan Foundry Limited, dropping the word 'company.' Vulcan locomotives were exported all over the world, with the first locomotives for Russia and Japan supplied in 1837 and 1871 respectively and a long association with India began in 1852. First World War production included shells, gun mountings and mine sweeping equipment. The first non-steam locomotive, an electric, was produced for India in 1929. The first diesel locomotive design commenced in 1932/33 and an agreement was reached with A/S Frichs in Denmark. The English Electric 6K engine was used from this time. The “Waltzing Matilda” tank was developed in 1938 and produced in large numbers and over five hundred ‘Austerity’ steam locomotives were produced for the War Department. Other wartime production included gun mountings and torpedo parts. In 1944 Vulcan acquired the locomotive business, Robert Stephenson & Hawthorns Ltd, based in Newcastle-upon-Tyne. In 1946 the company began working with the English Electric Company producing diesel and electric locomotives and became part of the English Electric Group in 1955. All locomotive building from Preston was transferred to Vulcan Foundry and Robert Stephenson’s in Darlington. Under the new ownership, the works produced many locomotives for both domestic and foreign railways, notably the Deltic. The mid-sixties saw the ‘RK’/’V’ engine production at Preston moved to Vulcan and Ruston & Hornsby Ltd merged with English Electric Diesels in 1966. After the General Electric Company plc (GEC) takeover in 1968 the Ruston name was used for some time inside what became GEC Diesels Ltd in 1975. Engine production and development continued for locomotive, industrial and marine applications until after the GEC-Alsthom merger in 1989. The company took over Mirlees Engines, Stockport in 1997 and was renamed Alstom Engines 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.

Crossley Motors began in 1902 as the vehicle manufacturing arm of Crossley Brothers Ltd. It was originally based at the Crossley Brothers works in Pottery Lane, Openshaw, Manchester. In 1906, the company was registered as the limited company Crossley Motors Ltd and moved to a site in Crossley Street, Gorton, Manchester the following year. The company produced cars from 1904 to 1937 and commercial vehicles from 1912 to 1956. The commercial vehicle developed in 1912 became the basis of the highly successful Royal Flying Corps (RFC) tender in the First World War. In the 1920s commercial vehicle production centred on military types; buses were introduced in 1928. In 1914 expansion of Crossley Brothers at Pottery Lane led to the acquisition of a second site at Errwood Park, Heaton Chapel, Stockport. Construction of the Errwood Park Works began in 1915, but the site was quickly given over to war work. Crossley Motors Ltd managed the National Aircraft Factory No. 2 on the site from 1917. After the First World War, the site became the works for Willys Overland Crossley before being sold to Fairey Aviation in 1934. After the Second World War, the Errwood Park Works became the permanent home for Crossley Motors Ltd. Crossley Motors was sold to Associated Equipment Company in 1948, and production continued at the Stockport site until 1958. The company ceased trading in 1966.