The Hillary Step, a rocky outcrop at 8,770m, just beneath the summit of Everest (8,850m), has finally succumbed to gravity and partially collapsed. At least it has according to mountaineer Tim Mosedale, who climbed the mountain this year. His claim has been refuted by the chair of the Nepal Mountaineering Association, however, sparking a debate which looks set to rage for some time yet. The definitive answer, after all, is located only a few metres short of the top of the world.