The 1921 British Mount Everest Reconnaissance Expedition set off to explore how it might be possible to get to the vicinity of Mount Everest, to explore possible routes for ascending the mountain, and – if possible – make the first ascent of the highest mountain in the world. At that time Nepal was closed to foreigners, so any approach had to be from the north, through Tibet. A feasible route was discovered from the east up the Kharta Glacier and then crossing the Lhakpa La pass northeast of Everest.
In January 1921 the Alpine Club and the Royal Geographical Society jointly set up the Mount Everest Committee to co-ordinate and fund the expedition. Although they initially supported an all-out attempt at the summit, members of the committee eventually agreed that the primary purpose of the mission should be reconnaissance.
The expedition set off in April 1921 – the climbing team consisted of two experienced mountaineers, Harold Raeburn and Alexander Kellas, and two younger men, George Mallory and Guy Bullock, both without any Himalayan experience. The expedition team also included Sandy Wollaston, a naturalist and doctor, Alexander Heron, a geologist, Henry Morshead and Oliver Wheeler, surveyors seconded from the army.
The expedition, having gathered Sherpas, Bhutias, porters, supplies and 100 Army mules (which later had to be replaced with hill mules and yaks), set off from Darjeeling in British India on 18 May 1921 for the 300-mile (480 km) march to Everest. The route took them through Sikkim – northeast through Tista valley, over the Jelep La into Tibet and on into the Chumbi Valley, passing Phari at 4,400 metres (14,300 ft), crossing the Himalaya watershed at Tang La and continuing to the Tibetan plateau. Then, leaving the Lhasa road and taking a westward course, the expedition reached Khamba Dzong. Here, on 6 June, Kellas died suddenly of heart failure and Raeburn became sick and had to return to Sikkim
The 1921 expedition was regarded as successful by experts as well as the general public with large numbers of people turning up for the official welcome home by the Royal Geographical Society and the Alpine Club at the Queen's Hall in London. Howard-Bury had become a celebrity. Speaking of the future summit attempt in his Queen's Hall address Mallory said he was "very far from a sanguine estimate of success ... A party or two arriving the top, each so tired that it was beyond helping the other, might provide good copy for the Press but the performance would provoke the censure of reasonable opinion".
Mallory had hoped to give up schoolteaching and to become a mountaineer and writer. When he provided his chapters for Howard-Bury's 1922 book of the expedition it had been on the clear understanding he would be paid. However, in 1923, three months before departing on the 1924 Everest expedition, he had still not received payment. When he pressed the Committee, they rescinded their agreement and said he would not be paid but nevertheless they "fully appreciated the value of your contributions". The 1924 expedition was the one from which he would not return, the identity of his remains being discovered in 1999. Bullock's expedition diary was published in 1962.