This is the extraordinary story of Hauptmann Herbert Cleff, who was captured in Egypt during the Allied advance from El Alamein in November 1942. He was thought to have had some administrative function in the Panzer corps, but not all was as it seemed.It was found that he had expert knowledge about tanks, and was interrogated both in the Western Desert Theatre and after transfer to the UK, following assessments that he might prove useful to the Allied war effort. He began to reveal tantalizing glimpses of advanced scientific and engineering projects back in Germany, including the development of a secret new fuel, and progress with submarines, jet-powered aircraft, faster-thansound flight and long-range offensive missiles. The truth of Cleff's revelations could not be fully verified at the time, but some were accepted by key experts, which led to the start of a Most Secret project for a British high-speed research aircraft. Eventually, he decided to collaborate fully with his captors, with a view to bringing the war to an earlier end, though always insisting that the object was to destroy the Nazi regime, to the advantage of Germany in the long run. He was released into civilian life in 1943, to undertake work for the Ministry of Supply. Information gathered in Germany after the War now allows comparisons to be made by which the veracity of Cleff's claims can be assessed. Some firm conclusions are reached, but the motivation for his actions remains elusive. This highly original account is sure to appeal to anyone interested in fresh and diverting contributions to the unfolding history of the Second World War.