Patrick Fairweather was born on 17 June 1936, son of John George Fairweather and Dorothy Jane (née Boanas). He was educated at Ottershaw School, Surrey, and Trinity College, University of Cambridge, studying history, and in 1962 married Maria Merica (who died in 2010), having two daughters.

After his National Service in the Royal Marines and Parachute Regiment, 1955-57, Fairweather entered the diplomatic service in 1965, and his career included the following: 2nd Secretary, Rome [Italy], 1966-69; Foreign and Commonwealth Office, 1969-70; 1st Secretary (Economic), Paris [France], 1970-73; FCO, 1973-75; 1st Secretary and Head of Chancery, Vientiane [Laos], 1975-76; 1st Secretary, UK Representation to EEC, Brussels, 1976-78; Counsellor (Economic and Commercial), Athens [Greece], 1978-83; Head of European Community Department (Internal), FCO, 1983-85; Ambassador to Angola, 1985-87; Assistant Under-Secretary of State, FCO, 1987-90; Deputy Under-Secretary of State (Middle East and Africa), FCO, 1990-92; Ambassador to Italy and (non-resident) to Albania, 1992-96.