Joining the Foreign Service in 1928, Mason had overseas postings to Brussels, Sofia, Prague, Ottawa, and Lisbon and also home posts at the
Foreign Office in London. He was assistant private secretary to the Foreign Secretary 1934–1936. Mason was private secretary to the
Parliamentary Under Secretary of State 1936–1937. He was an acting Counsellor in 1945. He was the British Minister at Sofia 1949–1951. Mason was recalled to London as assistant
Under Secretary of State at the Foreign Office from 1951 to 1954. He was
British Ambassador to the Netherlands 1954–1960. He was Permanent Representative on the North Atlantic Council 1960–1962. Mason was Alternate Delegate to the Minister of State in the Geneva Delegation on Disarmament and Nuclear Tests 1962–1964. In retirement, Mason was
High Sheriff of Nottinghamshire for 1970 and Treasurer of the
University of Nottingham from 1972 until his death. ==Family==