Tuhia he tomokanga mo tenei whitianga - I puta ia i te tekau ma rua o nga whakaaturanga i te IAAF World Cross Country Championships mai i te 1977 ki te 1995. Ko tana mahi takitahi i tae mai i te 1983 IAAF World Cross Country Championships
, i noho ai ia ki te whitu o te katoa. Ko Clarke te toa hiriwa e toru nga wa i te whakataetae (1982, 1987, 1989) me te wikitoria i te parahi a te roopu i te 1992, e tohatoha ana i nga honore me Mike McLeod, Hugh Jones, Julian Goater, Steve Kenyon, Karl Harrison, Carl Thackery, Kevin Forster, Steve Binns, Tim Hutchings, Gary Staines, Richard Nerurkar, me Eamonn Martin, me etahi atu.