Colossus computer
At this time the Colossus was still secret, long after any of its technical details were of any importance. This was due to the UK's intelligence agencies use of Enigma-like machines which they got other governments to buy. The agencies then broke the codes using  different ways. Had the knowledge of the codebreaking machines been widely known, no one would have accepted these machines; rather, they  would have developed their own methods for encryption, methods that the UK services might not have been able to break. The need for such  secrets slowly went away as communications moved to digital transmission and all-digital encryption systems became common in the 1960s.