An opera singer, who spied on the Germans for Britain, fooled Nazi secret police Gestapo by hiding secret documents in her underwear as she sang for Adolf Hitler at Berlin's Opera House, it has emerged. In fact, this incredible story of Brit Margery Booth's daring double-life has been revealed for the first time after a picture of her was put up for auction, 'The Sun' reported. Margery, who was married to German doctor Egon Strohm, stayed in Berlin when the World War II broke out and regularly performed for Hitler and the Nazi top brass at Berlin's famous Opera House. But she was also secretly meeting with British spy John Brown in Berlin gathering information on British traitors working for the Nazis. He passed on incriminating documents to Margery, who was the perfect agent because her popularity with Hitler and his henchmen put her above suspicion. Richard Westwood-Brookes, from auctioneer Mullock's, said: "On one occasion he passed her some documents just prior to a performance she gave to Hitler — and the papers were hidden in her underwear. "It was an incredibly brave thing to do. Towards the end of the war, John Brown's secret activities became known to the Nazis and Margery Booth was arrested and tortured by the Gestapo. "But she remained silent and without being able to prove anything the Gestapo finally let her go. She managed to escape Berlin during an air raid. It is quite astonishing her heroic activities are not widely known." The photo of Margery, who was born in Wigan, was taken at Freigegeben Stalag IIID PoW camp, where the Nazis hoped to recruit captured Brits. She had performed there and wrote on it: "With kindest remembrances. Good luck, Margery Booth." Margery died from cancer in 1952 aged 47.