Clark, born in London, attended
Dulwich Prep London and then
St Paul's School, London, where he took up running, as did his brothers Peter and Chris. Professionally, he worked as a labourer and hospital porter before becoming a history and physical education teacher. made twelve appearances at the
IAAF World Cross Country Championships from 1977 to 1995. Individually, his best performance came at the
1983 IAAF World Cross Country Championships, where he placed seventh overall. He ranked in the top twenty in the world over
10,000 metres in the
1982 season. He shares the
British record in the
ekiden marathon relay, alongside
Carl Thackery,
Jon Solly,
Mark Scrutton, and
Karl Harrison, with a silver medal-winning time of 1:59:14 hours set at the
1986 IAAF World Challenge Road Relay. In national competition he won the 5000 m title at the
1981 UK Athletics Championships, and was runner-up in that event at the
1983 AAA Championships. He won the
English Cross Country Championships three times (1982, 1987, 1988) and won the British Cross Country Championships in 1992. He was also twice runner-up at the British race and a four-time runner-up at the English Championships. He won the British Universities Cross Country Championships in 1981. At sub-national level he won the 1984 title in the
3000 metres at the South of England Athletics Championships and the 5000 m inter-county race at the 1985 CAU Championships. On the professional circuit he won races including the Cross di Volpiano, Amatrice-Configno, Foulée Suresnoise, 1989
Stockholm Marathon and the Cross de Nantes. He continues to take part in the sport as a
masters athlete, mostly in local
parkruns, though he completed the
2016 London Marathon in 3:03:54 hours. == International competitions ==