Government Communications Headquarters Tourist attraction in Cheltenham, United Kingdom

Alan Turing wrote two papers discussing mathematical approaches, titled The Applications of Probability to Cryptography and Paper on Statistics of Repetitions, which were of such value to GC&CS and its successor Government Communications Headquarters (GCHQ) that they were not released to the UK National Archives until April 2012, shortly before the centenary of his birth.

Source: Wikipedia

In the run-up to the Second World War, J. R. R. Tolkien was earmarked as a codebreaker. In January 1939, he was asked whether he would be prepared to serve in the cryptographic department of the Foreign Office in the event of national emergency. He replied in the affirmative and, beginning on 27 March, took an instructional course at the London HQ of the Government Code and Cypher School. A record of his training was found which included the notation "keen" next to his name,although Tolkien scholar Anders Stenström suggested that "In all likelihood, that is not a record of Tolkien's interest, but a note about how to pronounce the name." He was informed in October that his services would not be required.

Source: Wikipedia