It was the call the family of a young British climber who went missing on Everest 100 years ago had given up hope of ever getting.Last month, a team of climbers filming a National Geographic documentary stumbled on a preserved boot, revealed by melting ice on a glacier.This boot was believed to belong to Andrew Comyn "Sandy" Irvine, who disappeared while attempting to climb Everest in June 1924 with his partner George Mallory.What's more, it could potentially help solve one of mountaineering's biggest mysteries: whether or not the pair succeeded in becoming the first people to summit Everest, 29 years...