Christopher Hum was born on 27 January 1946, the son of Norman Charles Hum and Muriel Kathleen (née Hines). He was educated at Berkhamsted School, then Pembroke College, University of Cambridge (Foundation Scholar; 1st Class Honours; MA; Honorary Fellow 2004), later studying at the School of Oriental and African Studies, University of London (taking an MA in History of Art and Archaeology of E Asia, 2019). In 1970, he married Julia Mary, second daughter of Hon. Sir Hugh Park, having one son and one daughter.

Hum joined the Foreign and Commonwealth Office in 1967, and his diplomatic career included: Hong Kong, 1968–70; Peking [later Beijing], 1971–73; Office of the UK Permanent Representative to the EEC, Brussels, 1973–75; FCO, 1975–79; Peking, 1979–81; Paris [France], 1981–83; Assistant Head, Hong Kong Department, FCO, 1983–85; Counsellor, 1985; Deputy Head, Falkland Islands Department, FCO, 1985–86; Head, Hong Kong Department, FCO, 1986–89; Counsellor (Political) and Head of Chancery, UK Mission to UN, New York, 1989–92; Assistant Under-Secretary of State (Northern Asia), 1993–94, (Northern Asia and Pacific), 1994–95; Ambassador to Poland, 1996–98; Deputy Under-Secretary of State and Chief Clerk, FCO, 1998–2001; Ambassador to the People’s Republic of China, 2002–05.