Hayden Phillips was born on 9 February 1943, the son of Gerald Phillips and Dorothy Phillips. He was educated at Cambridgeshire High School, Clare College, University of Cambridge (MA) and Yale University, United States (MA). In 1967 he married (1st), Dr Ann Watkins (marriage dissolved), having one son and one daughter; and in 1980 (2nd), Laura Grenfell, having one son and two daughters.

Phillips joined the Home Office in 1967, and his career included the following posts: Assistant Principal, Home Office, 1967; Economic Adviser, Home Office, 1970-72; Principal, 1972-74; Assistant Secretary, and Principal Private Secretary to the Home Secretary (Roy Jenkins), 1974-76; Deputy Chef de Cabinet to President of the European Commission (Roy Jenkins), 1977-79; Assistant Secretary, Home Office, 1979-81, Assistant Under-Secretary of State, 1981-86; Deputy Secretary, Cabinet Office (MPO, subsequently Office of the Minister for the Civil Service), 1986-88; Deputy Secretary, Treasury, 1988-92; Permanent Secretary: Department for National Heritage, later Department for Culture, Media and Sport, 1992-98; Lord Chancellor's Department, 1998-2003; Department for Constitutional Affairs, 2003-04; Clerk of the Crown in Chancery, 1998-2004.