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.

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.