Colossus computer
Colossus plans and machinery were secret from the when they were made. They stayed so after the War, when Winston Churchill ordered the destruction of most of the Colossus machines into "parts no bigger than a man's hand"; Tommy Flowers himself burned  the designs in a fireplace at Dollis Hill. Some parts, changed to look innocent, were taken to Newman's Royal Society Computing Machine Laboratory at Manchester University. The Colossus  Mark 1 was taken apart and the parts were sent back to the Post Office. Two Colossus computers, along with two copied Tunny machines, were  kept.  They were moved to GCHQ's new head office at Eastcote in April 1946. They moved again with GCHQ to Cheltenham between 1952  and 1954. One of the computers, known as Colossus Blue, was taken apart in  1959; the other in 1960. In their later years, the computers were used for training. Before that, there had been  attempts to change them (sometimes well) for other purposes. Jack Good was the first to use it after the war, getting  NSA to use Colossus to do something for which they were planning to build a special purpose machine. Colossus  was also used to perform letter counts on one-time pad tape to test for non-randomness.