Leslie Fielding was born 29 July 1932, older son of Percy Archer Fielding and of Margaret (née Calder Horry). He was educated at Queen Elizabeth’s School, Barnet; Emmanuel College, University of Cambridge, the School of Oriental and African Studies, London and St Antony’s College, University of Oxford. In 1978, he married Dr Sally P. J. Harvey, sometime Fellow of St Hilda’s College, University of Oxford, having one son and one daughter.

After serving with the Royal Artillery, 1951-53 and the Territorial Army, 1953-56, Fielding entered the Diplomatic Service in 1956. His diplomatic career included: Tehran [Iran], 1957-60; Foreign Office, 1960-64; Singapore, 1964; Phnom Penh [Cambodia] (Chargé d’Affaires), 1964-66; Paris [France], 1967-70; Deputy Head of Planning Staff, Foreign and Commonwealth Office, 1970-73; seconded for service with European Commission in Brussels [Belgium], 1973; Director (External Relations Directorate General), 1973-77; permanent transfer to European Commission, 1979; Head of Delegation of Commission in Tokyo [Japan], 1978-82; Director-General for External Relations, Brussels, 1982-87.