1921 - 1953
Led by Colonel Charles Howard-Bury and including George Mallory, the British Expedition discovers a route from the East Rongbuk Glacier to North Col, reaching 23,030 ft.
2nd British expedition
Led by General Charles Granville Bruce, and again including Mallory. The team become the only humans ever to climb above 26,000ft, using oxygen for the first time to reach 27,300 ft.
3rd British expedition
Led by Lt Col Edward Norton. Mallory and Irvine make their fateful attempt on the summit but do not return. Norton reaches 28,126 ft without oxygen, just 900 ft short of the summit.
Led by Bill Tilman and including Eric Shipton. The North Col is reached from the west for the first time and the team continues to over 27,200 ft without supplemental oxygen.
Led by Edouard Wyss-Dunant and including Tenzing Norgay. The expedition attempts to summit Everest via the South Col and reaches 28,199 ft, just 500 ft short of the South Summit.
Led by John Hunt. Edmund Hillary and Tenzing Norgay achieve first ascent, reaching the summit at 11:30 a.m. May 29. They spend 15 minutes on the rooftop of the world.