Looks at the breaking of Shark and other Fish codes with the use of the Tunny machine and the development of Colossus which was to be the world's first electronic programmable computer. All these efforts lead to the shortening of the war by several years. In order to keep the secret of 'Ultra' safe, all of the machines and paperwork were destroyed at the end of the war. However, that's not quite all of the story...
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