“Some 480 suspected enemy spies were detained in Britain in the course of the war. Just 77 of these were German. The rest were, in descending order of magnitude, Belgian, French, Norwegian, and Dutch, and then just about every conceivable race and nationality, including several who were stateless. After 1940, very few were British. Of the total intercepted, around a quarter were subsequently used as double agents, of whom perhaps 40 made a significant contribution.”

“Some 480 suspected enemy spies were detained in Britain in the course of the war. Just 77 of these were German. The rest were, in descending order of magnitude, Belgian, French, Norwegian, and Dutch, and then just about every conceivable race and nationality, including several who were stateless. After 1940, very few were British. Of the total intercepted, around a quarter were subsequently used as double agents, of whom perhaps 40 made a significant contribution.”

— Ben Macintyre