Cynics today call it the human conveyor belt. Some years, around 40 climbing teams pit themselves against the world's highest mountain, often littering the snowy wilderness with their discarded equipment. Of those who tread the now well-trodden paths, as many as two thirds can expect to reach the top.
But in the early 1950s, with the 8,850m summit still unconquered, it was a different story. In those days, they called Everest the Third Pole, and the competition between nations to go where no human had gone before resembled the race for the Moon.
It was in 1852 when a British government survey of India established that the mountain called Peak XV, but known locally as "Goddess Mother of the World", was in fact the highest point on the planet. Fourteen years later, it was renamed after Sir George Everest, a former surveyor general of India .
Straddling the border between Nepal and Tibet, the mountain rises to a pair of summits that reach two-thirds of the way through the earth's atmosphere to a point where temperatures and oxygen levels are so low and winds are so high that no plant or animal can thrive.
The first attempt to climb Everest was in 1920. Between then and 1952, seven subsequent attempts on the Northeast Ridge and three on the Southeast all failed, beaten by the appalling conditions, difficult terrain and effects of thehigh altitude.
But with improved equipment came more intense competition. And in the race for Everest, as in the race for space, timing was everything. For not only was climbing limited to a tiny springtime window, but each assault had to obtain permission from the Nepalese government and then wait its turn.
Flustered by the near-success of the Swiss in 1952, the British knew that their 1953 attempt had to be a success. Nobody could be sure when they would get another crack at it. And besides, this was to be Coronation year.
When the expedition's sponsors, the Royal Geographical Society and the Joint Himalayan Committee of the Alpine Club, decided to replace the popular explorer Eric Shipton as leader with the military mountaineer Colonel John Hunt, there was an outcry. But Hunt had a reputation for getting things done, and he quickly assembled a strong team. This included not only old hands, but also student mountaineers (George Band was only 22) and Commonwealth climbers such as New Zealanders Edmund Hillary and George Lowe, and Tenzing Norgay, then a resident of India.
Once on the mountain, the team pioneered a new passage through a treacherous area of ice and on to the South Col, a rocky ridge 8,000m up.
On May 26, they made their first attempt on the summit. Using "closed circuit" breathing apparatus, a system that mixed pure oxygen with recycled air, Charles Evans and Tom Bourdillon made it past the Swiss high-point of the previous year, climbing to within 100m of the summit before one of their oxygen sets malfunctioned. Now it was the turn of Hillary and Tenzing Norgay.
They decided to break their ascent in a camp high above the South Col, setting out again at dawn for the final push. In places, the Southeast Ridge seemed razor thin in the early morning light, but by 9am they had reached the lower of the two summits. A long, looping ridge lay ahead, with steep slopes on one side and overhanging snow on the other. After an hour on this treacherous path, they arrived at what they feared might be an insurmountable obstacle - a steep, rocky step twice the height of a house.
It was Hillary who found a crack in the face, and managed to haul himself through it with Tenzing Norgay close behind (the climb is still called Hillary's Step). By 11.30, they had reached the end of the ridge. "A few more whacks of the ice axe in the firm snow, and we stood on top," said Hillary later. Tenzing Norgay flung his arms around his shoulders and thumped him on the back, and the two stood for a while on the highest point of the planet before beginning their descent.
It was a non-climbing member of the team, The Times correspondent James Morris - now known as the travel writer Jan Morris - who contrived to get a coded message back to London so that the news would break on Coronation day. But while the young Queen Elizabeth bestowed knighthoods on Hunt and Hillary, Tenzing Norgay had to make do with a British Empire Medal. In the 1950s, it seems, some mountains were still harder to climb than others.
As news of their successful ascent broke around the world, the lives of Hillary, Tenzing Norgay and Hunt changed for ever. Hunt, the expedition leader, became The Lord Hunt of Llanvair Warterdine, an international ambassador known for his work with young people and with the Parole Board.
"It was my ambition just as much as everybody else's in the party to be first at the top," he told an interviewer in 1978. But he kept himself out of the two summit teams, believing that his role as a co-ordinator would be more important to the team. He died in 1998, aged 88.
President Nehru called upon Tenzing Norgay to "train a thousand Tenzings", and so Norgay set up the Indian Mountaineering Federation while devoting himself to a life as unofficial ambassador for the Sherpa people. Although he never learned to write, he spoke seven languages, and dictated several books about a bygone age of mountaineering. Tenzing Norgay, who died in 1986, remained in close contact with Hillary for the rest of his life.
Hillary has also held ambassadorial positions, and is currently New Zealand's ambassador to India. In the years after his historic ascent of Everest, he turned his attention to Antarctica, becoming the first person after Scott to reach the South Pole overland. But in later years, his energies have largely been devoted to improving the lot of the Nepal's Sherpa community, and in particular its young - or Hillary's Children, as they are sometimes known. Money from his Himalayan Foundation helps pay for projects ranging from teacher training to reforestation and the repair of Buddhist monasteries, and Hillary has become one of the most influential figures in the region surrounding Everest. However, he has written about being "racked by guilt" over his part in paving the way for the army of trekkers and climbers who descended on the area after the building of an airfield in 1964. Many of the outsiders stripped forests for firewood and stole from Sherpa homes.
On the morning of June 6, 1924, two British climbers tucked into a breakfast of tinned sardines before setting out for the summit of the world's highest mountain. For 38-year-old George Leigh Mallory, this was his third attempt at Everest.
In 1921, he had been part of a British team that had set a new 24,600ft record on the mountain, and that record had yet to be broken. On previous climbs, Mallory had disdained to use the bottled gas that the local guides referred to as "English air", considering it unsporting. But today, he came equipped with oxygen apparatus, and a climbing partner, 22-year-old "Sandy" Irvine, who was adept at repairing what was still unreliable and weighty equipment. Shortly after setting off from their camp at the top of the North Col, and with an estimated three days' climbing ahead of them, they passed another member of the team, Howard Somervell, and he loaned his camera to Mallory. It was to be the last contact anybody had with with the climbing partners.
Two days later, Mallory and Irvine were spotted. The geologist Noel Odell was following on behind, and he saw them - mere dots on the skyline - through the early afternoon mist. Odell watched them approach and climb a rock step called the Second Step, close to the base of the summit pyramid.
They were "going strong", he reckoned, and he felt certain they would make it. But whether they did climb to the summit, almost 30 years ahead of Hillary and Tenzing Norgay, is a mystery that has yet to be solved. In 1975, a body, thought to be that of Irvine, was found by a Chinese climber, and in 1999, a US-led expedition found Mallory's body, 600m from the summit. But Somervell's camera, which could solve the mystery once and for all, has yet to turn up. The search continues.
Around 120,000 ethnic Sherpas live in the Himalayan region, 120,000 in the Indian state of Sikkim and the remainder in Nepal. Despite the influx of climbers and trekkers in recent decades, their culture, which is Tibetan in origin, survives intact.
Sherpa yak-trains still transport buffalo hides, salt and wool between India and Tibet across mountain passes nearly 20,000 feet above sea level.
Yaks are central to the traditional Sherpa way of life, providing wool, leather, fuel, fertiliser, dairy products and meat. Another major source of food, alongside rice and lentils, is the potato, which was introduced from English gardens in Darjeeling and Kathmandu in the 1800s.
The remarkable ability of Sherpas to function at high altitudes has made them invaluable to climbing expeditions ever since an Aberdeen physiologist, Dr A.M. Kellas, recognised their hardiness at the turn of the last century. Kellas taught chemistry at Middlesex Hospital, but would spend several months every year exploring the Himalayas with the assistance of local people.
In the 1920s, it became customary to hire porters and mountain guides from among the expatriate Sherpa community in Darjeeling, Nepal at that time being out of bounds to Westerners. Many Sherpas would make their way from Nepal to Darjeeling in search of mountaineering work, among them the young Tenzing Norgay, who moved to India in 1933. Two years later, at the age of 19, he was chosen by Eric Shipton to take part in a recognisance of Everest. After nearly 20 expeditions, "Sherpa" Tenzing, as he became known, was to join John Hunt's successful team as a climber.
Tackle Everest today and you will sport a different outfit for each stage of your ascent. By the time you approach the summit, you will resemble a space explorer, with face-mask, glacier-goggles, oxygen canister and harness all made from super-strong, lightweight materials.
Even Hillary and Tenzing Norgay had specially insulated boots and clothing.
But for the early pioneers, wool, linen and leather were the chief ingredients, and in the 1920s, when Mallory and Irvine tackled the climb, the most advanced kit available consisted of a windproof smock made from the tightly-woven "Willesden canvas" that was used for aeroplane wings.
The first oxygen systems were not only prone to failure, but were twice as heavy as their modern equivalent, and carrying the cylinders probably used up all the extra energy that their contents provided. Similarly, a cotton frame-tent weighed 10kg, compared with 4kg for today's far stronger model, and even a wooden-handled ice-axe was twice as heavy as its state-of-the-art successor. Thanks to near-weightless materials, today's climbers think nothing of adding radios, satellite phones and digital cameras to their list of must-pack items, whereas even in Hillary's day the decision to include radio equipment cannot have been taken lightly.
ROLL OF HONOUR
First ascent: Edmund Hillary and Tenzing Norgay, 1953.
First ascent without additional oxygen: Reinhold Messner and Peter Habeler, 1978.
First solo ascent (without oxygen): Reinhold Messner, 1980.
First ascent by a woman: Junko Tabei (Japan), 1975.
Most ascents (10): Ang Rita Sherpa (all without oxygen), 1983, 1984, 1985, 1987, 1988, 1990, 1992, 1993, 1995, 1996.
Oldest climber: Ramon Blanco (Spain) 60 years and 160 days, 1993.
Youngest British climber: Edward Grylls (23), 1998.
First disabled climber: Tom Whittaker, 1998.