In August 1946 the United States passed the 'McMahon Act', stopping its wartime collaboration with Britain on nuclear weapons.
From June 1947, Britain began the development of its own atomic bomb under the Ministry of Supply Research Division at Woolwich and the Armament Research Establishment [ARE] at Fort Halstead in Kent.
On 1 April 1950, high explosive research [HER] work (the expression used to signify atomic weapons research) was moved from ARE Fort Halstead to a new site at Aldermaston, near Reading in Berkshire (previously an aircrew holding centre for the Royal Canadian Air Force). Other research on the British atomic weapons programme, carried out at the Armament Research Establishment in Kent, was transferred to Aldermaston in the same year. In charge was Dr William Penney, who had been one of the British scientists at Los Alamos during the war. To make the core for the weapon, new facilities for handling plutonium were needed, but Fort Halstead was too small. In September 1949, an airfield near the village of Aldermaston in Berkshire was allocated. On 1 April 1950, it re-opened as the headquarters of the British atomic weapon programme. The Atomic Weapons Research Establishment (AWRE) was established on 1 April 1950, by the Ministry of Supply, at the former RAF Aldermaston airfield.
Its first Director was William Penney. In 1954 AWRE was transferred to the newly created United Kingdom Atomic Energy Authority (UKAEA). Whereas in 1971, the production activities of UKAEA were transferred to the newly-created British Nuclear Fuels Ltd (BNFL), in 1973 AWRE was transferred to the Procurement Executive of the Ministry of Defence.
Parts of AWRE's weapons production processes were carried out at two Royal Ordnance Factories (ROFs): ROF Burghfield and ROF Cardiff. In 1984 these were separated from the other factories which formed into a government-owned defence company, Royal Ordnance plc and was privatised in 1987. ROF Burghfield and ROF Cardiff remained within the Procurement Executive and came under the control of AWRE.
In 1987, AWRE was combined with ROF Burghfield and ROF Cardiff to form the AWE. The latter sites being renamed AWE Burghfield and AWE Cardiff (the latter was closed in 1997). AWE Burghfield, a former munitions factory, occupies a 225 acre site and is responsible for the complex final assembly and maintenance of the warheads while in service, as well as their decommissioning. It remained with the Ministry of Defence, Procurement Executive.
However, in 1989, the UK government announced its intention to find a suitable private company to run AWE under a Government Owned/Contractor Operated (GO-CO) arrangement. In 1993 the government awarded a contract to Hunting-BRAE, a consortium of Hunting Engineering, Brown and Root and AEA Technology. In 1999 Hunting-BRAE lost the contract to AWE Management Ltd, (AWE ML) a consortium of BNFL, Lockheed Martin and Serco which assumed responsibility on 1 April 2000. This did not represent privatisation, the Ministry of Defence owns all the AWE sites and a Golden Share in AWE plc. In December 2008, it was announced that the BNFL share in the management company had been sold by the British government to Jacobs Engineering Group, an American engineering services company.
AWE plc is responsible for the day-to-day operations of AWE. AWE plc is owned by the British Government and managed by Jacobs Engineering Group, Lockheed Martin UK and Serco through AWE Management Ltd who hold a 25 year contract (until March 2025).
Other Atomic Weapons Establishment sites could be found at ROF Burghfield, Burghfield and ROF Cardiff, Llanishen, Cardiff, the former Royal Ordnance Factories; Orford Ness and Foulness Island. The ROF Cardiff, Orford Ness and Foulness Island sites are now closed.