Milner-Barry was born 20 September 1906, the son of Professor E. L. Milner-Barry. In 1947 he married Thelma Tennant Wells and they had one son and two daughters. He died 25 March 1995. Milner-Barry studied classics at Trinity College, Cambridge. He began by working for a firm of stockbrokers, 1929-38. He was one of the senior code-breakers at Bletchley Park, 1940-45. He was Gordon Welchman's deputy at Bletchley Park and was primarily responsible for the vital "cribs" of Hut 6 and in 1943 he took over responsibility for Hut 6. On 21st October 1941, Milner-Barry along with Alan Turing, Gordon Welchman, Hugh Alexander wrote directly to Churchill to seek more staff for Bletchley Park. Milner-Barry delivered the letter personally to 10 Downing Street and Churchill gave them his support. Milner-Barry had a lifelong interest and talent in chess - he was British Boy Champion, 1923 and also a member of the British International teams, 1937-61. He was playing chess for Britain in Argentina when war broke out, and worked as Chess Correspondent for "The Times" newspaper 1938-45. After the war he was Principal, HM Treasury, 1945, and became Assistant Secretary in 1947. He was Director of Organisation and Methods, Treasury, 1954-58, Director of Establishments and Organisation, Ministry of Health, 1958-60, and Under-Secretary, Treasury, 1954-66.