Kamilisha sentensi ifuatayo: Yeye alifanya maonyesho kumi na mbili katika IAAF World Cross nchi Championships kutoka 1977 hadi 1995. Moja kwa moja, utendaji wake alikuja katika
1983 IAAF World Cross nchi Mashindano, ambapo yeye kuwekwa saba jumla. Clarke alikuwa medali ya fedha mara tatu katika mashindano (1982, 1987, 1989) na pia alishinda shaba ya timu mwaka 1992, kushiriki heshima na Mike McLeod, Hugh Jones, Julian Goater, Steve Kenyon, Karl Harrison, Carl Thackery, Kevin Forster, Steve Binns, Tim Hutchings, Gary Staines, Richard Nerurkar, na Eamonn Martin, miongoni mwa wengine.