His ascent in 1976 of the West Face of Changabang (6864m), which neighboured Dunagiri, saw his first partnership with Peter Boardman, and was widely acclaimed as a bold, magnificent feat of mountaineering. Tasker made an unsuccessful attempt on Nuptse with Doug Scott and Mike Covington in the autumn of 1977, and he and Boardman were invited to the K2 expedition led by Chris Bonington in 1978, which was abandoned after Nick Estcourt was killed in an avalanche.