When mountain climber Simon Yates cut the rope and sent his friend and climbing partner Joe Simpson plummeting to an ordeal few mountaineers can have contemplated, the outcome was totally unpredictable. That Simpson survived his experience on Peru's Siula Grande is a revelation of the power of the human spirit to overcome fear, pain and deprivation of almost unimaginable intensity. He did not expect to live it all over again - more than once. The...