Michael Loewe relates his personal experience of work at Bletchley Park during WW2. The high-level intelligence produced at Bletchley Park, codenamed Ultra, provided crucial assistance to the Allied war effort. Sir Harry Hinsley, a Bletchley veteran and the official historian of British Intelligence during the Second World War, believed that Ultra shortened the war by two to four years and that the outcome of the war would have been uncertain without it.