Nicholas Fenn was born on 19 February 1936, son of the Reverend Professor J. Eric Fenn and of Kathleen (née Harrison). He was educated at Kingswood School, Bath and Peterhouse College, University of Cambridge. In 1959, he married Susan Clare (née Russell), having two sons and one daughter.
After his National Service as a Pilot Officer in the RAF, 1954-56, Fenn joined the Diplomatic Service in 1959, and his career included the following posts: Third Secretary, British Embassy, Rangoon [Burma], 1959-63; Assistant Private Secretary to Secretary of State for Foreign and Commonwealth Affairs, 1963-67; First Secretary, British Interests Section, Swiss Embassy, Algiers [Algeria], 1967-69; First Secretary (Public Relations), UK Mission to United Nations, New York [United States], 1969-72; Deputy Head, Energy Department, Foreign and Commonwealth Office, 1972-75; Counsellor, Peking [China], 1975-77; Head of News Department and FCO Spokesman, 1979-82; Spokesman to last Governor of Rhodesia, 1979-80; Ambassador to Rangoon, 1982-86; Ambassador to Dublin [Ireland], 1986-91; High Commissioner in New Delhi [India], 1991-1996.
Sir Nicholas was awarded the GCMG in 1995 (KCMG 1989; CMG 1980).