Edmund Hillary and Tenzing Norgay were the first to reach the summit of Mount Everest on May 29, 1953. But three days earlier, two other climbers came within one hundred metres of the top.

shrimpo1967, CC BY-SA 2.0, via Wikimedia Commons
Next year will be the 60th anniversary of the first successful summit of the highest peak on Earth (depending, of course, on how you measure “highest”). Edmund Hillary and Tenzing Norgay, the mountaineers who first reached that lofty peak are household names. History, however, was almost very different. But for a single equipment failure, two other climbers would have reached the summit three days before Hillary and Norgay.
The 1953 British expedition to Mount Everest was a large one: eleven British mountaineers, two New Zealand mountaineers, two Nepalese Sherpa mountaineers, twenty more Sherpa guides, and 362 porters to carry all their stuff as far up the mountain as possible.
Conscious of the difficulties of high altitudes, the expedition also carried a new and innovative oxygen tank system. A British climber and physicist named Tom Bourdillon (along with his father) had invented a closed-circuit oxygen apparatus that would help the team survive long enough to reach the top. Bourdillon was part of the expedition.
The Bourdillons’ experimental closed-circuit system was completely closed off from the outside air. Climbers inhaled pure oxygen from a tank, and when they exhaled the result went through a filter to scrub out the carbon dioxide and recycle the oxygen for later. Because the climbers were breathing pure oxygen, they got an incredible speed boost. But the experimental system was complicated and prone to failure.
In contrast, an open-circuit system mixed tank oxygen with the air outside. When a climber breathed out, that breath (and any remaining oxygen) was lost to the atmosphere. So, no big speed boost, but greater reliability.
The leader of the British expedition, John Hunt, decided to try both methods. The first attempt on the summit would use the closed-circuit system. If it failed, the second and third attempts would use open circuits.
The first team was Bourdillon and the expedition’s deputy leader, Charles Evans. They set out for the final summit on May 26, 1953. Flush with pure oxygen, the two mountaineers climbed at the ridiculous rate of 300 metres an hour, and by 1pm that day they reached the South Summit. At the time, no-one had ever climbed higher.
The main summit was just one hundred metres further up, across an extremely narrow ridge and over the Hillary Step. But, just at that crucial last stage, disaster. Evans’ closed-circuit system broke down and could not be fixed. Thwarted and exhausted, the two climbers had to return. The ascent of Everest was almost in their grasp, but some bad luck and bad timing ended the attempt.
The second team, Hillary and Norgay, set out the next day. On an open-circuit system they moved much slower, but on May 29 they reached the top, and history. Bourdillon died young, in a climbing accident; Evans went on to lead the team that first successfully summited Kangchenjunga, the third highest mountain peak.