However unorthodox his operation, it worked. His listeners never set eyes on a single German PoW, but eavesdropped on more than 10,000. They picked up enormously valuable intelligence on the secret weapons programme that produced the V1 and V2 rockets; on battle plans and troop positions; and on U-boat bases and new aircraft technology. ‘You have done a Herculean task,’ Kendrick was told towards the end of the war. It was on a par with the better-known work at Bletchley Park.
Helen Fry’s richly researched book, brimful of surprising and fascinating detail, will bring the secret listeners some of the attention they deserve.