Tommy Flowers

Tommy Flowers went to work for the General Post Office in 1926, and in 1930 joined the GPO's Research Section at Dollis Hill.  He was a visionary, and foresaw an age in which electromechanical telephone exchanges could be replaced by purely electronic exchanges using valves.  During the Second World War he was one of the Dollis Hill specialists selected to support work at Bletchley Park.  He met Alan Turing who introduced him to Max Newman.  Newman led the area which was trying to automate the processes involved in the cryptanalysis of the Lorenz SG40/42 online telecipher device codenamed TUNNY at Bletchley Park.

Flowers was involved in the construction of the Heath Robinson machine, but used the insights he had about the design of electronic telephone exchanges to think of a complex valve-based machine: this was COLOSSUS, the forerunner of the modern computer, and Flowers led the team which built it.  Even before the first COLOSSUS had been built, he was adding improvements to COLOSSUS 2. Eventually, ten COLOSSUS machines were built, and their output provided vital intelligence for the Military, particularly before D-Day. After the war eight of the machines were dismantled so that the parts could be recycled, but GCHQ kept two for its own use. 

Tommy Flowers returned to the Post Office and resumed his work on electronic exchanges.  Because of the continuing sensitivity about cryptanalytic success during the war, and particularly the use of computers in cryptanalysis, he had retired before the story of his crucial role in the development of modern computing could be told.