This is Peter Calvocoressi's amazing book Top Secret Ultra (1980) which is one of only three books about Bletchley Park to be written by someone working there in a senior capacity for virtually the whole war. Bletchley Park, a modest estate some fifty miles northwest of London, was the site of one of the closest-held and longest-kept secrets of World War II. Most Secret Ultra, renamed Top Secret Ultra when America joined the venture, conveyed a staggering amount of intelligence on enemy movements and intentions to Allied field commanders. This was obtained by steady monitoring of German radio transmissions, and was made possible by a major feat in scientific detection - the breaking of the German Enigma machine ciphers. Calvocoressi, who is well known as an author, publisher, and authority on international affairs, was part of and eventually head of air intelligence at Bletchley. In this engaging memoir, he opens a window on scientific intelligence that gives a rare view of those who have labored in its service. Schoolmasters and university professors, mathematicians, chess players, businessmen, writers, even museum curators, devoted days and nights for years to the arduous tasks first of wresting the secrets from the Enigma machine, then of piecing together the jumbled letters into serviceable military data. The inside view is engrossing. The overview, a thoughtful assessment of the uses and importance of Ultra on several hattlefronts and in some of the important campaigns of the war, is uncommonly rewarding. Devoid of inflated claims and heroics, it conveys an exceptional picture of the supportive, sometimes peripheral, occasionally decisive role that intelligence operations can play. Top Secret Ultra presents an informed assessment of how the decrypted information helped the Allies bring the war to an end. 140 pages, many pictures. A must read for everyone.