In 1951 the 1945–51 Labour Government nationalised most large British iron and steel companies under the Iron & Steel Act 1949. The Parkgate company became part of the resulting Iron and Steel Corporation of Great Britain. After the 1951 General Elections the 1951–57 Conservative Government privatised most of the corporation, and in 1956 Parkgate was sold to Tube Investments. Major development work was planned for a site at Aldwarke, to begin production in the 1960s. This included Kaldo process basic oxygen steelmaking plant which was fed from the blast furnaces at Parkgate, ladles being moved by rail between the sites. This development also included hot rolling facilities. By the 1970s demand had changed and part of the old plant was demolished, the remainder of the Parkgate site was closed in 1985 with the closure of the heat treatment dept. In 1976 rolling capacity was increased with the coming on stream of the Thrybergh Bar Mill.