GC&CS also produced secure codes for the Allies
This work was originally carried out at Broadway Buildings in London, the pre-war home of GC & CS. When the codebreakers moved to Bletchley Park, a separate team of 20 code makers known as the ‘Code and Cipher Production Unit’ moved to Mansfield College Oxford. The team later grew to around 40 staff, led by Royal Navy Pay Commander Edward Hok.
The team were responsible for producing ‘communications security materials’, which included cipher keys, code books, and one time pads. The latter involved compiling long lists of random numbers, a time consuming and tedious task. One advantage of being in Oxford was that the team were near the Oxford University Press, who were able secretly to print copies of the the codes and ciphers, as well as printing forms and documents required by the Codebreakers at Bletchley Park.