Anthoine was a good technical rock climber and made a number of first ascents in North Wales, the best known of which was The Groove on Llech Ddu, a crag on the north side of Carnedd Dafydd. However, it was for his mountaineering that he is best remembered. In the Alps he was involved in a six-day struggle through a storm near the summit of Mont Blanc which killed seven climbers, cajoling others to survive.