'Big Ben' was a British operation to consider the possibilities of countermeasures against the V-2 ballistic missile, and also to establish the feasibility of a system to provide early warning of missile attack (autumn/winter 1944).

Much of the work was undertaken by Supermarine Spitfire F.Mk 16 single-engined fighters of No. 602 Squadron, and the effort was also based initially on the reconstruction and evaluation of captured German missiles. On 31 July 1944, after the UK agreed to exchange Spitfire fighters for the wreckage of a V-2 which had come down in Sweden during a German trial, specialists at the Royal Aircraft Establishment, at Farnborough in Hampshire, began an attempt to reconstruct the missile. Late in the same month the Polish resistance movement’s 'Most III' undertaking was able to capture an intact V-2 near the Pustkow testing centre in German-occupied Poland. The missile had been launched on a test flight, which failed and caused the missile to fall but without exploding. The Poles recovered the intact missile from the Bug river, and its key elements were transferred secretly to the UK.