Stephen Gomersall was born on 17 January 1948, the son of Harry Raymond Gomersall and Helen Gomersall. He was educated at Forest School, Snaresbrook, then Queens’ College, University of Cambridge (Modern Languages, MA), also taking an MA at Stanford University, California (1970). He was married in 1975 (marriage dissolved 2006), having two sons and one daughter.

Gomersall entered the Diplomatic Service in 1970, and his diplomatic career included: Tokyo, 1972–77; Rhodesia Department, FCO, 1977–79; Private Secretary to Lord Privy Seal, 1979–82; 1st Secretary (Political) Washington [United States], 1982–86; Economic Counsellor, Tokyo, 1986–90; Head of Security Policy Department, FCO, 1990–94; Deputy Permanent Representative, UK Mission to UN, 1994–98; Director, International Security, FCO, 1998–99; Ambassador to Japan, 1999–2004.