The 100-year-old mystery of mountaineers George Mallory and Andrew Comyn “Sandy” Irvine may be moving closer to being solved. The partial remains of the 22-year-old mountaineer who disappeared during the British Everest expedition in 1924 are believed to have been found. During an expedition last month, a National Geographic documentary crew discovered an old, worn leather boot with steel nails. Inside the shoe was a frozen human foot wrapped in a sock with the name “AC IRVINE” embroidered on it.

Andrew “Sandy” Irvine’s foot is believed to have been found on Mount Everest

In September, the team, consisting of photographer and director Jimmy Chin and filmmakers and mountaineers Erich Roepke and Mark Fisher, ventured onto the vast expanse of the central Rongbuk Glacier beneath the north face of Mount Everest. “I lifted the sock,” Chin said, describing the moment.

“And there's a red label that says AC IRVINE sewn into it,” he continued, adding that he and his companions realized what the discovery meant. “We were all literally running in circles dropping f-bombs,” Chin added.

The discovery could potentially help solve a centuries-old mystery surrounding Irvine's disappearance and determine whether he and his partner Mallory managed to reach the summit before their deaths.

If they had made it to the summit without losing their lives on the descent, they would have achieved the incredible feat 29 years before Sir Edmund Hillary and Tenzing Norgay.

Chin's team had previously found an oxygen cylinder dated 1933 near the central Rongbuk glacier, likely from the fourth British Everest attempt. The discovery of the partial remains of Irvine is one of the biggest breakthroughs in the great Everest mystery. While Mallory's remains were found in 1999, Irvine's were unknown.

“It's the first real evidence of where Sandy landed,” Chin said. “Many theories have been put forward,” he continued, adding that he hopes the discovery might help provide some clarity to Irvine's family, who have volunteered DNA samples.

“When someone goes missing and there is no evidence of what happened to them, it can be very challenging for families. And it's certainly helpful to have some definitive information about where Sandy might have landed, and also an important clue to the climbing community about what happened,” Chin said.