James Mellon was born on 25 January 1929. He was educated at Glasgow University (MA), and in 1956 married: 1st, Frances Murray (she died in 1976), having one son and three daughters; 2nd, in 1979, Mrs Philippa Shuttleworth (née Hartley).

Mellon's career included: Department of Agriculture for Scotland, (1953-60); Agricultural Attaché, Copenhagen [Denmark] and The Hague [Netherlands], (1960-63); Foreign Office, (1963-64); Head of Chancery, Dakar [Senegal], (1964-66); UK Delegation to European Communities, (1967-72); Counsellor, (1970); Head of Science and Technology Department, Foreign and Commonwealth Office, (1973-75); Commercial Counsellor, East Berlin [Germany], (1975-76); Head of Trade Relations and Export Department, FCO, (1976-78); High Commissioner in Ghana and Ambassador to Togo, (1978-83); Ambassador to Denmark, (1983-86); Director-General for Trade and Investment, United States, and Consul-General, New York, (1986-88).