She only took up mountaineering in the early 1950s.[2] In 1959 she went to the himalaya as a member of the International Women's Expedition to Cho Oyu, 8,188 m (26,864 ft) and the sixth-highest mountain in the world,[10] and Darvall handled much of the pre-expedition arrangements.[2] The all female team also included Loulou Boulaz from Switzerland, Dorothea Gravina and Eileen Healey from the UK, and the french mountaineers Claudine van der Straten, Jeanne Franco, Colette LeBret, Micheline Rambaud and Claude Kogan, who was the overall leader. Amongst the Nepali members were Tenzing's daughters Nima and Pem-Pem and his niece Dhoma. Loulou Boulaz and Margaret Darvall were seriously ill and had to be evacuated to Namche Bazar accompanied by LeBret the doctor.[11] Whilst they were at Namche Bazar, the Sherpa Sirdar Wongdi and Chowang were buried by an avalanch a little above Camp III, although Wongdi freed himself after a two-hour struggle Chowang could not be rescued. The expedition leader, Claude Kogan, with Claudine van der Stratten and the Sherpa Ang Norbu had established Camp IV at 23,300 ft (7,100 m) on 1 October but a spell of bad weather separated them from the rest of the party and after the weather had improved a search, on 4 October, found no trace of the camp leading to the conclusion that the camp and its occupants had been overwhelmed by an avalanche.[12]
Undettered by the losses on Cho Oyu, in 1963 Darvall embarked on an expedition to Turkey's Taurus Mountains. There were no maps, and the country was empty apart from Kurdish brigands who attacked and robbed the party, despite these difficulties they successfully climbed the peak of Mount Erciyes and then went on to climb Demirkazık by the SE ridge.[5]
Later, in 1968, she joined the Women's East Greenland Mountaineering Expedition to the Stauning Alps. The party included Joan Busby (leader), Esme Speakman, Mary Fulford and Eilith Nisbet and they undertook a number of climbs in the area around Bersærkerbræen.[13]
Darvall was elected president of the Pinnacle Club and president of the Ladies' Alpine Club (1973–1975).[14][5] The merger of the Ladies' Alpine Club with the UK Alpine Club took place during her presidency,[15] "the merger might well not have taken place but for the brilliant strategies of Margaret, together with Janet Carleton, and the LAC might have been allowed just to wither away."[5] In 1976, soon after the merger, Darvall was voted on to the committee of the Alpine Club.[5]