 Millar was also the United Kingdom Deputy at the North Atlantic Council from 1950 to 1952 and its Representative thereon from 1952 to 1953.The latter year Millar was appointed High Commissioner to the British Zone of occupied Germany, a post he held until 1955, and was then Ambassador to West Germany from 1955 to 1956.After his return to Britain he served as Permanent Under-Secretary at the Foreign Office from 1957 to 1962.