The decision to build an atomic weapon is often ascribed to a Cabinet meeting with some rather colourful comments from the Foreign Secretary, Ernest Bevin. As is often the case, the truth is rather more prosaic.
The decision to build the piles at Windscale to produce plutonium makes little sense unless an atomic weapon was intended. At the time, however, no formal decision had been taken, and at the end of 1946, the Controller of Atomic Energy, Lord Portal, felt that matters should be put in hand. In conjunction with the Chiefs of Staff, he wrote a memo to the Prime Minister, Clement Attlee, asking permission to go ahead with the design and construction of an atom bomb.
At the same time, he asked William Penney to draw up the necessary plans and organisation. Penney at this time was Chief Superintendent Armaments Research (CSAR). First of all, he drew the organisation that would be needed, with an estimate of the staff required:
In a further memo, he went into greater detail as to what was required:
The initial work on the design and construction was carried out at Fort Halstead in Kent. The move to Aldermaston came in 1950.