Colossus Mark II
Designed by Tommy Flowers at the Post Office Research Station, Dollis Hill.
The world's first programmable electronic computer, using 2,400 vacuum tubes (valves).
It read cipher tape at 5,000 characters per second through an optical reader,
comparing patterns against hypothesized Lorenz wheel settings.
10 Colossi were built. Their existence was kept secret until the 1970s. All were dismantled after the war on Churchill's orders. Tommy Flowers was never properly recognized in his lifetime, and had to take out a personal loan to fund the project.