Hawker Siddeley Group PLC was initially formed as the Hawker Siddeley Aircraft Company on 11th July 1935. The new company was established to acquire all of the shares of the Armstrong Siddeley Development Company and 50% of the shares of the Hawker Aircraft Company. This merged the two largest British aircraft manufacturers and included the subsidiaries of the two companies involved. These consisted of Armstrong Siddeley Motors, Sir W.G. Armstrong Whitworth Aircraft Ltd and A.V. Roe and Co, which were part of the Armstrong Siddeley Development Company, and the Gloster Aircraft Company, which was part of Hawker, all of which continued to produce aircraft under their own names.

During the Second World War Hawker Siddeley was one of the most important aircraft manufacturers in Britain. During the course of the conflict it produced several important designs including the Hawker Hurricane and Avro Lancaster as well as working on Britain’s first jet aircraft, the Gloster E.28/39, and the first British jet fighter, the Gloster Meteor. In 1945 the company also purchased Victory Aircraft from the Canadian government and transferred to its subsidiary Avro. This then became A.V. Roe Canada but was most often know as Avro Canada.

On 22nd June 1948 the company underwent a restricting when it was transformed from a private to a public limited company and underwent a name change. As such it went from being Hawker Siddeley Aircraft Company Limited to Hawker Siddeley Group Limited.

In 1957 the Hawker Siddeley Group purchased the Brush Group, which included Brush Electrical Machines and Brush Traction. At the time it also acquired Mirrlees, Bickerton and Day. It also formed Hawker Siddeley John Brown Nuclear Construction as a joint venture to produce nuclear power equipment for marine propulsion, electrical generation and other industrial applications. In 1958 it formed another join company this time with Beyer Peacock, under the name Beyer Peacock (Hymek) Ltd, in order to manufacture diesel hydraulic locomotives. 1959 saw a further joint company, Primapax, which made, hired and sold vending machines.

During the late 1950s the British government decided that the number of aircraft manufacturers should be decreased as the number of contracts being offered was being reduced. As a result of this Hawker Siddeley merged all of its aviation interests, Hawker, Avro, Gloster, Armstrong Whitworth and Armstrong Siddeley, into a single division, Hawker Siddeley Aviation during October 1958. In 1959 it also merged its aircraft engine business, Armstrong Siddeley, with Bristol Aero Engines to form Bristol Siddeley Engines. The group also acquired Folland Aircraft and in 1960 purchased both the de Havilland Aircraft Company and the Blackburn Group.

By 1961 the Hawker Siddeley Group was made up of 3 major operational groups, Hawker Siddeley Aviation, Hawker Siddeley Industries and A.V. Roe Canada. Avro Canada would be dissolved in 1962 due to the cancellation of the Avro Arrow aircraft with its remaining assets being transferred to Hawker Siddeley Canada. The new company focused on the manufacture of railway vehicles, subway cars and trams.

In 1963 the group underwent a further restructuring as the names of its constituent companies were dropped in favour of a single Hawker Siddeley branding. As a result, the company’s products were rebranded with a HS number in place of their previous number. During 1968 the group expanded further by acquiring Crompton Parkinson, which was later combined with Brook Motors, when they acquired this company in 1970, to form Brook Crompton.

On 29th April 1977 the Hawker Siddeley Group underwent a major change when, as a result of the Aircraft and Shipbuilding Industries Act, its Aviation and Dynamics groups were nationalised and merged with the British Aircraft Corporation and Scottish Aviation to form British Aerospace. Despite this loss of its aviation interests, they only accounted for 25% of the group’s business and as such it was able reorganise its remaining interests in a holding company, Hawker Siddeley Group PLC. The decision was taken to focus this group on railway engineering, industrial electronics and signalling equipment.

During the 1980s the Hawker Siddeley Group continued to expand, acquiring Carlton Industries between 1981 and 1984, and GEC Small Machines Company and GEC Alsthom Electromotes in 1989. This success made the group a target for a hostile takeover by the BTR conglomerate and in November 1991 they acquired it for £1.5 billion. The Hawker Siddeley name continued to be used in the group’s switchgear division which was later sold to FKI and later Melrose PLC.