Christie was born 27 January 1881 in Edgbaston, Warwickshire. He gained a first class Chemistry degree at Aachen University, Germany. He joined the Royal Flying Corps, 1914-18, and continued when it became the Royal Air Force, 1919-30. He was the Air Attaché in Washington, 1922-1926, and the Air Attaché in Berlin, 1927-1930. He retired from active employment due to ill health in 1930. From 1934 he investigated the political situation in Germany and Central Europe on behalf of Sir Robert Vansittart. He had valuable contacts, from his work, in Germany, Austria and the Sudetenland. He would spend a number of months of the year in Germany and at times also acted as an intermediary between local parties. As the situation in Europe became more precarious Christie gathered more of his information from anti-Nazi informants with German government contacts of their own. The most significant of his informants was Hans Ritter (aliases included Johnnie, Knight, and Kn). Christie died on 3 November 1971.