Military intelligence, grossly neglected in the interwar period, had by mid-1942 proved itself an indispensable instrument of war through the exploitation of radio intelligence derived from decrypts ('Ultra') of the supposedly unbreakable German Enigma cipher. Ralph Bennett, who worked for four years as a senior producer of Ultra at Bletchley Park, illustrates in this collection some of the steps by which he and others developed a new type of history from an archive they had themselves created. This new history, based on practical utility being the primary concern of intelligence, spurned the concept of 'must have been' and rigidly separated supposition from securely ascertained fact. In further essays he goes on to tackle subjects as disparate as the battle of Crete (1941) and the integration of decrypt intelligence with that from double-cross agents. At the end of his fascinating account, he concludes that his wartime experiences have left him with an enhanced regard for strict logical proof - the sine qua non of military intelligence - and with the conviction that historians should shun the speculation which mars so much 'ordinary' history.