The world altitude record was not broken again until the British expeditions to Mount Everest, and would then become the exclusive preserve of climbers on the world's highest mountain. On the the record was broken twice. On 20 May, George Mallory, Howard Somervell and Edward Norton reached on the mountain's North Ridge, without using supplemental oxygen. Three days later George Finch and Geoffrey Bruce, using supplemental oxygen, followed the same route and went even higher—turning around at about when Bruce's oxygen apparatus failed.