In October, it began nightly bombing attacks from St. Eval, Cornwall, on German shipping and docks at Brest, France.
It was detached from its base in Rutland to St Eval in Cornwall, and on the very first occasion that it operated from there, 17 July, a crew captained by Flight Lieutenant PR Casement (Lancaster I R5724) became the first Bomber Command crew to bring back irrefutable evidence that they had destroyed a U-boat at sea, in the form of a photograph showing the U-boat crew in the water swimming away from their sinking vessel.
Five widely dispersed cottages, two houses and portions of two farms were acquired by compulsory purchase; the village of St Eval was completely demolished in order to build the airfield.