'This was a mountain that he had to climb': How Hillary and Tenzing survived the 'death zone' to conquer Everest

To reach Everest's summit Edmund Hillary and Tenzing Norgay had to climb sheer rock, while battling treacherous ice and a deadly lack of oxygen on the most dangerous part of the mountain. Seventy-two years ago, they shared their victory with the BBC.

"I think my first reaction was definitely one of relief," New Zealander Edmund Hillary told the BBC on 3 July 1953, as he described how he and Nepalese sherpa Tenzing Norgay felt when they stood on the highest point on Earth. "Relief that we had found the summit for one thing and relief that we were there." Tenzing too, having survived the precarious icy terrain and the biting cold, said through his translator, the expedition's team leader Colonel John Hunt, that his first feeling on reaching the top was "immense relief", followed by joy. This was because in order to stand on Everest's summit the two men had managed to scale a seemingly insurmountable sheer 40ft vertical rock face in the mountain's most treacherous region – the infamous "death zone".

The mountain, which towers 8,849m (29,032ft) above sea level, straddling the border of Nepal and Tibet, goes by many names. The British named it after surveyor George Everest in 1856, but it has long been known locally as Sagarmatha in Nepal and is called Chomolungma, meaning goddess mother of the world, in Tibet.

The death zone was a term given to a particular section of Everest by Edouard Wyss-Dunant, a doctor who led the Swiss attempt to scale it in 1952. Tenzing had been a member of this expedition, too. The moniker refers to the altitude that climbers reach on the mountain – 8,000m (26,000ft) above sea level – where the low-oxygen atmosphere starts to have disastrous effects on their physiology and their cells start to die. The majority of the climbers who have died on Everest have met their end in the death zone.

Humans have simply not evolved to survive in the incredibly cold temperatures, brutal winds and lack of oxygen that exists there. The thinness of the atmosphere means that mountaineers suffer hypoxia, where their vital organs do not get enough oxygen and bodies begin to break down. As their brains and lungs get starved of oxygen, their heart rate spikes, increasing their risk of a heart attack. The shortage of oxygen to the brain causes it to swell, triggering headaches, nausea and quickly impairing a climber's judgment and ability to make decisions, especially when they are under stress. As their brains swell, mountaineers have been known to experience delirium, talking to people who aren't there, burrowing in the snow or even shedding their clothing.

Tenzing and Hillary – along with the others on the expedition – had planned for this slowly acclimating themselves to the harsh conditions in the Himalayas by establishing a series of camps at increasing altitudes, gradually making their way up the mountain through April and May, 1953. This allowed their bodies time to expand their lung capacity and produce more haemoglobin – the protein in red blood cells that helps carry oxygen from the lungs to the other parts of the body – to compensate for the decreasing oxygen as they moved towards Everest's peak. But this acclimatisation was also not without risk for the team as too much haemoglobin thickens the blood. This makes circulation more difficult, which increases the likelihood of a stroke and accumulation of fluid in the lungs.

However, it is virtually impossible to acclimatise your body at any altitude above 6,000m (19,700ft) and the vertical rock face they needed to scale that sat 8,790m (28,839ft) above sea level. So, the climbers had brought with them specially designed oxygen apparatus, which would help combat the effects of the altitude's atmosphere. But they were under no illusion about the magnitude of the challenge facing them. Three days earlier the expedition's primary climbing team, Tom Bourdillon and Charles Evans, came within 100m (328 ft) of the summit. But, exhausted by the climb, beset by malfunctioning oxygen sets and battered by freezing winds, they had been forced to turn back before reaching the top.

In the early hours of 29 May 1953, Tenzing and Hillary began the expedition's second attempt, battling their way through the snow along the exposed ridgeline towards the peak. As they scrambled over icy ridges, the New Zealand mountaineer started having his own doubts about if they could go on, Hillary's son, Peter, told BBC Witness History in 2023.

"One of the things I most is his description of moving up the steep snow and ice flanks up towards the south summit. He says he was out in front, cutting these steps, great sheet of snow and ice breaking loose, and just taking off down these steep slopes into the Kangshung Face (eastern-facing side) of Everest dropping down into Tibet. And he said, and I have seen it in his diary as well, he started having some doubts about the conditions, whether it was safe to go on," he said. "I always him telling this story with a twinkle in his eye and a wry smile, and he looked down at Tenzing and he said they both smiled at each other and kept on going despite those conditions."

Hillary’s climbing companion Tenzing felt it was his destiny, that he "had a calling for this mountain. It was a special mountain for him," his son Jamling Norgay, told BBC Witness History in 2023. "He had tried to climb this mountain six times already over a period of over 21 years. The attempt one year before with the Swiss he had reached almost 400m from the summit and had to turn back. He always felt this was a mountain that he had to climb," he said.

The exposed sheer vertical rock face was the last major barrier that stood between the two climbers and their goal. Its smooth surface with seemingly no foot or hand holds, appeared impossible to climb. With a rope attached to him held by Tenzing, Hillary wedged his body into a narrow crack between the rock face and an adjacent ridge of ice, praying that the ice didn't give way. He then slowly and painstakingly inched his way up. When he reached the top, he threw down the rope to Tenzing who followed him up. The rock face he had managed to shimmy up would later be named the Hillary Step in his honour. It was destroyed by a devastating earthquake in 2015.