 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.A small team consisting of Tasker, Boardman, and Doug Scott made an ascent of Kangchenjunga (at 8,598 m the third highest mountain in the world) by a new route from the North-West in 1979 (with Georges Bettembourg also on the team but not making the summit); this was also the first ascent of the mountain without the use of supplementary oxygen.