Derek Tonkin was born on 30 December 1929, the son of Henry James Tonkin and Norah Wearing. He was educated at High Pavement Grammar School, Nottingham, and St Catherine’s Society, Oxford. In 1953 he married Doreen Rooke; they have one son and two daughters (and one son deceased).

After completing his National Service (1948-49), Tonkin joined the Foreign Office in 1952. His diplomatic career included: Warsaw [Poland], (1955); Bangkok [Thailand], (1957); Phnom Penh [Cambodia], (1961); FO, (1963); Warsaw, (1966); Wellington [New Zealand], (1968); Foreign and Commonwealth Office, (1972); East Berlin [Germany], 1976; Ambassador to Vietnam, (1980-82); Minister, Pretoria [South Africa], (1983-86); Ambassador to Thailand, and concurrently to Laos, (1986-89).