Dudley Clarke, working undercover as a correspondent for The Times, had been running a strategic deception section in the Middle East since 1940.
In October 1941 he was arrested in Madrid dressed - 'down to a brassiere' - as a woman. He told Spanish police that he was a novelist who wished to study the reactions of men and women in the street but he told the British consul that he was taking feminine garments to a lady in Gibraltar and thought he would try them on 'for a prank'.
The police apparently considered it a 'homosexual affair' and released him but the Germans were convinced they were onto a 'first class espionage incident'. Cadogan advised the Embassy in Madrid that they should 'get him to Gibraltar by quickest means'.
The file contains two photographs of him, including one in women's dress.