Project E was a joint project between the United States and the United Kingdom during the Cold War to provide nuclear weapons to the Royal Air Force (RAF) until sufficient British nuclear weapons became available. It was subsequently expanded to provide similar arrangements for the British Army of the Rhine. A maritime version of Project E known as Project N provided nuclear depth bombs used by the RAF Coastal Command.
The British nuclear weapons project, High Explosive Research, successfully tested a nuclear weapon in Operation Hurricane in October 1952, but production was slow and Britain had only ten atomic bombs on hand in 1955 and fourteen in 1956. The Prime Minister of the United Kingdom, Winston Churchill, approached the President of the United States, Dwight D. Eisenhower, with a request that the US supply nuclear weapons for the strategic bombers of the V bomber fleet until sufficient British weapons became available. This became known as Project E. Under an agreement reached in 1957, US personnel had custody of the weapons, and performed all tasks related to their storage, maintenance and readiness. The bombs were held in secure storage areas (SSAs) on the same bases as the bombers.
The first bombers equipped with Project E weapons were English Electric Canberras based in Germany and the UK that were assigned to NATO. These were replaced by Vickers Valiants in 1960 and 1961 as the long-range Avro Vulcan and Handley Page Victor assumed the strategic nuclear weapon delivery role. Project E weapons equipped V-bombers at three bases in the UK from 1958. Due to operational restrictions imposed by Project E, and the consequential loss of independence of half of the British nuclear deterrent, they were phased out in 1962 when sufficient British megaton weapons became available, but remained in use with the Valiants in the UK and RAF Germany until 1965.
Project E nuclear warheads were used on the sixty Thor Intermediate Range Ballistic Missiles operated by the RAF from 1959 to 1963 under Project Emily. The British Army acquired Project E warheads for its Corporal missiles in 1958. The US subsequently offered the Honest John missile as a replacement. They remained in service until 1977 when Honest John was superseded by the Lance missile. Eight-inch and 155 mm nuclear artillery rounds were also acquired under Project E. The last Project E weapons were withdrawn from service in 1992.
Background
During the early part of the Second World War, Britain had a nuclear weapons project codenamed Tube Alloys. At the Quebec Conference in August 1943, the Prime Minister of the United Kingdom, Winston Churchill, and the President of the United States, Franklin Roosevelt, signed the Quebec Agreement, which merged Tube Alloys with the American Manhattan Project to create a combined British, American and Canadian project. The September 1944 Hyde Park Aide-Mémoire extended commercial and military cooperation into the post-war period. Many of Britain's top scientists participated in the Manhattan Project. The Quebec Agreement specified that nuclear weapons would not be used against another country without mutual consent. On 4 July 1945, Field Marshal Sir Henry Maitland Wilson agreed on Britain's behalf to the use of nuclear weapons against Japan.
The British government considered nuclear technology to be a joint discovery, and trusted that America would continue to share it. On 16 November 1945, President Harry S. Truman and Prime Minister Clement Attlee signed a new agreement that replaced the Quebec Agreement's requirement for "mutual consent" before using nuclear weapons with one for "prior consultation", and there was to be "full and effective cooperation in the field of atomic energy", but this was only "in the field of basic scientific research". The United States Atomic Energy Act of 1946 (McMahon Act) ended technical cooperation. Its control of "restricted data" prevented US allies from receiving any information. Fearing a resurgence of American isolationism, and Britain losing its great power status, the UK government restarted its own development effort, now codenamed High Explosive Research.