Flowers was speaking in his quiet, modest way (writes Jack Copeland). He was telling me about the giant electronic computer he had built for codebreaking during the war. The story was riveting. “There should be a book about Colossus”, I suggested.“A book about Colossus...”, he said softly, almost disbelievingly. His computer's role in the Allied victory had been secret for so long. I began the search for the codebreakers who could provide the rest of the complex picture. People said “We can‘t talk about a lot of it—Official Secrets Act”. But then British Intelligence declassified a crucial wartime report: 500 pages of previously ultra-secret material. Suddenly doors opened and tongues loosened. More...