James Hennessy was born on 26 September 1923, the son of Richard George Hennessy, DSO, MC. He was educated at Bedford School and King’s College, Newcastle, before going on to Sidney Sussex College, University of Cambridge and the London School of Economics. In 1947 he married Patricia Unwin (who died in 2015), elder daughter of Wing Commander F. H. Unwin, OBE, and they had five daughters (and one son deceased).

Hennessy served in the Royal Artillery, 1942-44, and was seconded to the Indian Army, 1944-46, as Adjutant and Battery Commander, in the 6th Indian Field Regiment. After the war he was appointed to the Overseas Service in Basutoland [later Lesotho], serving as: District Officer, 1948; Judicial Commissioner, 1953; District Commissioner, 1954-56; Joint Secretary, Constitutional Commission, 1957-59; Supervisor of Elections, 1959; Secretary to Executive Council, 1960; seconded to Office of High Commissioner, Cape Town/Pretoria [South Africa], 1961-63; Permanent Secretary for local government, 1964; MLC, 1965; Secretary for External Affairs, Defence and Internal Security, 1967; Prime Minister’s Office, 1968.

Hennessy retired from the Overseas Service in 1968, not long after Basutoland gained independence, and was later appointed to the Diplomatic Service: Foreign Office, 1968-70; Chargé d’Affaires, Montevideo [Uruguay], 1971-72; High Commissioner to Uganda and Ambassador (non-resident), Rwanda, 1973-76; Consul-General, Cape Town, 1977-80; Governor and Commander-in-Chief, Belize, 1980-81. Following the end of his time in the Diplomatic Service, Hennessy became Chief Inspector of Prisons for England and Wales, 1982-87.

Sir James died on 25 February 2024.