A fter a day spent hiking across the Col d’Entrèves glacier, a sugar hit is required. I descend on the cable car and join the queue at the ice-cream counter. Above me, surrounded by jagged peaks, looms the huge white figure of Mont Blanc, serene and pure against a brilliant blue sky. Although it’s late afternoon, people are still heading up the mountain, and there are two clear groups. On one side are the tourists, who are about to be lifted into unfamiliar frozen realms at 3,375 metres (11,072ft), hoping to grab a picture and return. Mixed among them are the weathered faces of mountain experts: hikers confidently heading for a high-altitude hut, or climbers with coils of rope. How many of those tourists, I wonder, are wishing they could be mountaineers, secretly regretting the twists of fate that kept them away from that path? But all is not lost. The aspiring adventurer, no matter what age or background, can begin the journey to competence in the mountains.…