Title: The Ultra secret
Subjects: British Personal narratives, Cryptography, Secret service, World War, 1939-1945, World war, 1939-1945, miscellanea, World war, 1939-1945, secret service, great britain, World war, 1939-1945, cryptography, World war, 1939-1945, personal narratives, british
Places: Great Britain
People: F. W. Winterbotham (1897-)