He studied at the University of Wales (1961-1966), Indiana University in America under Dave Baker (1966-1967), and then at York University (1967-1970).
He began learning the piano at the age of six, and began playing jazz as early as the age of 13. Alongside his studies he played jazz professionally, with Evan Parker (1966) and then with his own trio (1967-1976), with Barry Guy on bass and Alan Jackson, Jon Hiseman, and Tony Oxley for periods on drums. Additionally he worked with John McLaughlin (1968), the London Jazz Composers Orchestra (1970-1980s), and with Oxley"s ensemble (1972-1981).
He and Guy worked in a trio with Philosophy Wachsmann from 1976 well into the 1980s, and played solo piano throughout North America and Europe.
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.
From 1985 he worked in a trio setting with Jeff Clyne and Tony Levin. Riley has taught at the Guildhall School of Music and Drama and currently teaches at Goldsmiths, University of London, where he has taught continuously since the 1970s.