Denis Doble was born on 2 October 1936, son of Percy Claud Doble and Dorothy Grace (earlier Dorothy Petley). He was educated at Dover Grammar School, then New College, Oxford, studying history. In 1975 he married Patricia Ann Robinson, havng one daughter and one son.

After a spell in the Royal Air Force (1955-57), Doble joined the Colonial Office (1960-64), serving as Assistant Private Secretary to Duncan Sandys, the Commonwealth and Colonial Secretary from 1963 to 1964. When the Colonial Office was phased out, Doble joined the Diplomatic Service in 1965 and his career with the Foreign and Commonwealth Office included: First Secretary in Brussels [Belgium] (1966-68) and Lagos [Nigeria] (1968-72); South Asian and Defence Departments, FCO (1972-75); First Secretary (Economic), Islamabad [Pakistan] (1975-78); Head of Chancery, Lima [Peru] (1978-82); East African Department, FCO (1982-84); Acting Deputy High Commissioner, Bombay [India] (1985); Deputy High Commissioner for Calcutta (1985-87), then Kingston [Jamaica] (1987-91); Consul-General, Amsterdam [Netherlands] (1991-96).