Bryan Cartledge was born on 10 June 1931, the son of Eric Montague George Cartledge and Phyllis (née Shaw). He was educated at Hurstpierpoint and then St John's College, Cambridge (becoming an Honorary Fellow in 1985). In 1960 he married (1st), Ruth Hylton Gass, daughter of John Gass, having one son and one daughter (marriage dissolved 1994); then in 1994 (2nd), Dr Freda Gladys Newcombe.
After his national service in the Queen's Royal Regiment, (1950-51) and a year as a Commonwealth Fund Fellow at Stanford University, (1956-57), Cartledge became a Research Fellow at St Antony's College, Oxford (1958-59), working on the memoirs of Sir [Robert] Anthony Eden [later 1st Lord Avon]. He then entered the Diplomatic) Service in 1960 and served in the following posts: Foreign Office Northern Department, (1960-61); Stockholm [Sweden], (1961-63); Moscow [Soviet Union], (1963-66); Diplomatic Service Administration Office, (1966-68); Tehran [Iran], (1968-70); on sabbatical, Harvard University, (1971-72); Counsellor, Moscow, (1972-75); Head of East European and Soviet Department, Foreign and Commonwealth Office, (1975-77); Private Secretary (Overseas Affairs) to the Prime Minister [James Callaghan and Margaret Thatcher], (1977-79); Ambassador to Hungary, (1980-83); Assistant Under-Secretary of State, FCO (Arms Control), (1983-84); Deputy Secretary of the Cabinet, (1984-85); Ambassador to the Soviet Union, (1985-88). Following his retirement from the Diplomatic Service, Cartledge became Principal of Linacre College, Oxford, from 1988 to September 1996.