Stuart Milner-Barry - Bletchley Park

Bletchley Park

Upon their return, all three soon joined the Government Code and Cypher School (GC&CS) at Bletchley Park. Milner-Barry was recruited by mathematician Gordon Welchman, who had been his contemporary at Trinity College; in turn Milner-Barry recruited Hugh Alexander. Arriving in early 1940, he joined Welchman's "Hut 6" section, whose task was to solve the Enigma cipher machine as used by the German Army and Air Force.

In 1993, Milner-Barry wrote that "to this day I could not claim that I fully understood how the machine worked, let alone what was involved in the problems of breaking and reading the Enigma cipher". Nonetheless, with his knowledge of the German language, he made a study of the decrypts and found that they contained stereotyped patterns and forms of address that could be exploited as "cribs" – reliable guesses for the plain language message that matched a given piece of encrypted text. Finding reliable cribs was a critical task for Hut 6, as Enigma was broken primarily with the aid of "bombes", large electromechanical machines which automatically searched for parts of the correct settings. Bombes were reliant on a suitable crib in order to succeed. In autumn 1940, Milner-Barry was put in charge of the "Crib Room".

He was billeted with Alexander, who was working in Hut 8, the counterpart to Hut 6 working on German Naval Enigma. Their close friendship let them easily resolve the competing needs of their sections for the limited available bombe time. By October 1941, he was deputy head of Hut 6 under Welchman. At this time, Bletchley Park was experiencing a shortage of clerical staff which was delaying the work on Enigma, and the management of GCCS appeared unable to obtain the resources needed. This affected both Hut 6 and Hut 8, which was run by mathematician Alan Turing with Hugh Alexander as his deputy. Together, Welchman, Milner-Barry, Turing and Alexander bypassed the chain of command and wrote a memorandum directly to the Prime Minister, Winston Churchill, outlining their difficulties. It fell to Milner-Barry to deliver the message to 10 Downing Street in person, on 21 October 1941. The next day, Churchill responded, "Action this day: Make sure they have all they want on extreme priority and report to me that this has been done." Within a month their needs were being met.

In autumn 1943, Milner-Barry took over as head of Hut 6, which by that time had grown to over 450 staff, Welchman having been appointed the Assistant Director of Mechanisation at Bletchley Park. He remained in charge until the end of the war, presiding over a number of technical challenges presented by the introduction of extra security devices to the German Enigma, including the Enigma Uhr and a rewireable "reflector" rotor. His entry in the Oxford Dictionary of National Biography notes that, "although he increasingly felt that Hut 6 was on the verge of losing the ability to decode Enigma, it held on until the end of the war, and this was due in no small part to his gifted leadership." The official history of Hut 6, written immediately after the end of World War II, comments on his early "most vital technical achievement" in finding cribs, and on his "administrative and diplomatic talents" in his later role as head of the section.