George Leigh Mallory was the only climber to take part in all three of the British pioneering expeditions to Mount Everest in the 1920s. Born in 1886, he died a few days short of his 38th birthday, while making a summit attempt with his young companion, Andrew Irvine.

Mallory was the son of a clergyman, an idealist and a romantic, and he was married with three small children. A schoolmaster by profession, he switched in 1923 from teaching boys to teaching adults, which he found very rewarding. During the Great War of 1914-18 he had served at the front as a gunner. He was a neat and bold rock climber and a competent ice climber, but his greatest assets were vivacity and a love of adventure. He would seize the moment and encourage his fellow climbers to follow. If he had a weakness, it was the failure to recognize when he had given enough. He was charismatic and endearingly absent-minded, though this could have proved a fatal flaw.

Those who set off on the reconnaissance trip of 1921 had no idea what they were up against. But as Mallory put it, "to refuse the adventure is to run the risk of drying up like a pea in its shell." They were walking off the known map, with high hopes of scaling a mountain no Westerner had ever seen at close quarters, venturing into atmospheres thinner than anyone had climbed into before. For its day, going to Everest was like going to the moon. The small, poorly equipped little band, dressed in an assortment of tweeds and home-knits, challenged Himalayan heights with little to assist them beyond the indomitable spirit of Empire.

Though visible as a small bump on the horizon from the Indian hill station of Darjeeling, Everest had remained remote because it straddled the border between Tibet and Nepal and both countries were at the time strictly out of bounds to travelers. Having at last negotiated permission to enter Tibet, the expedition set off on a six-week approach march, exploring and surveying as they went, and carrying out a "photographic offensive" on the mountains and medieval culture of rural Tibet.

With his friend Guy Bullock, Mallory shouldered the lion's share of exploration. The two tramped prodigious distances, up peaks and glaciers; they waded torrents and inspected valleys in their quest to unlock the secrets of the Everest region. They were prepared to leave the mighty East Face of Everest with its thundering avalanches for "other men, less wise" and, peering over Lho La into the Western Cwm and the broken Khumbu Icefall, they were relieved that this dangerous and laborious-looking possibility of a route lay across the border in forbidden Nepal.

It was the North Col which held the key, of that they were sure, although strangely their peregrinations had not revealed the easiest way to approach it. (It fell to E.O. Wheeler, one of the Survey of India officers accompanying the expedition, to discover that a small, insignificant-looking side stream flowing into the main Rongbuk Valley was in fact the outlet of the East Rongbuk Glacier, coming down in a great arc from the col.) Instead, Mallory and Bullock led a small group to the North Col by a long route from the east, over the Lakpa La. They breasted the col in a fierce gale and were soon forced back the way they had come, but although conditions were unfavorable for a proper attempt on the mountain that year, Mallory was convinced that a clear route existed all the way to the summit.

The following year a stronger climbing team, approaching along the East Rongbuk valley, was able to push on to a height of 27,000 feet, higher than anyone had climbed anywhere, but still 2,000 vertical feet short of the highest summit in the world. Mallory decided on one last attempt before the expedition left for home, but he set off up the slopes of the North Col too soon after fresh snow and a massive avalanche swept away nine men, killing seven of them, all Sherpa. The loss of "these brave men" left him crushed with guilt for they were, he felt, "ignorant of mountain dangers, like children in our care."