[1][2] He was the elder son of Marjorie (nee Emmott), a secretary, and her husband, John Riley, an engineer and part-time dance band leader.

[1] Alongside his studies he played jazz professionally, with Evan Parker (1966) and then with his own trio (1967–76), with Barry Guy on bass and Alan Jackson, Jon Hiseman, and Tony Oxley for periods on drums.

From 1978 to 1981, he played in a quartet with Guy, Trevor Watts, and John Stevens; in the early 1980s he did duo work with Keith Tippett, with Jaki Byard, and with Elton Dean.

Riley taught at the Guildhall School of Music and Drama and at the Goldsmiths, University of London, having started his tenure during the 1970s.

[3][4] His partner of 29 years was Annie Garrett, a former actor and drama teacher, who helped set up the Brit school, and he had three stepchildren.