[3] After leaving the seminary he first worked as a dustman before studying sociology at Manchester University, where he was an enthusiastic participant in the Student Union's gypsy liaison and soup-run groups.

[3] His ascent in 1976 of the West Face of Changabang (6864m), which neighboured Dunagiri, saw his first partnership with Peter Boardman,[3] 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.

In the winter of 1980–1981 Tasker was part of an eight-man team (with Alan Rouse, John Porter, Brian Hall, Adrian Burgess, Alan Burgess, Pete Thexton and Paul Nunn) attempting to make a difficult winter assault on the West Face of Mount Everest; this was unsuccessful but was recounted in Tasker's first book Everest the Cruel Way.

[5] In 1981, he was part of the British team which made the first ascent of Kongur Tagh (7,649 m) in China, accompanied by Chris Bonington, Peter Boardman and Alan Rouse.