Tommy Flowers (1905–1998) was the visionary engineer from the British Post Office who brought the speed of light to codebreaking. When Bletchley’s mathematicians were stymied by the complex Lorenz cypher, Flowers proposed a radical solution: a machine built with thousands of vacuum tubes.
In 1943, he delivered Colossus, the world’s first large-scale electronic digital device. Using 1,500 glowing tubes, it made mechanical machines obsolete and bridged the gap between the age of brass and the age of electrons. Because of the Official Secrets Act, Flowers’ role remained hidden until the 1970s.