He made his way to Switzerland and, after securing his son Egon's release from Germany, he moved to Britain, where he was imprisoned after the outbreak of the Second World War. He was later moved to a prison camp in Canada. In 1942, Hanfstaengl was turned over to the US, worked for US President Franklin Roosevelt's "S-Project" and revealed information on approximately 400 Nazi leaders. He provided 68 pages of information on Hitler alone, including personal details of Hitler's private life, and he helped Professor Henry Murray, the director of the Harvard Psychological Clinic, and psychoanalyst Walter Charles Langer and other experts to create a report for the Office of Strategic Services, in 1943, designated the "Analysis of the Personality of Adolph Hitler". In 1944, Hanfstaengl was handed back to the British, who repatriated him to Germany at the end of the war. William Shirer, a CBS journalist who resided in Nazi Germany until 1940 and was in frequent contact with Hanfstaengl, described him as an "eccentric, gangling man, whose sardonic wit somewhat compensated for his shallow mind".