Dave Pearce spent only 20 minutes on the top of Mount Everest

Warrant officer Dave Pearce, 39, from Budleigh Salterton, and his sherpa, Chhring Dorje, scaled 29,000 feet (8,839 meters) to the top of the Himalayan mountain.

But within 20 minutes, Mr Pearce had to begin his descent to help two climbers from another expedition in a major rescue operation.

The men, a Briton with a broken leg and an Australian with snow-blindness and frostbite, are now being helped back down to Camp 5 at 26,000 feet (7,924 meters).

They are currently at death zone - where the body starts to deteriorate because of the lack of oxygen Major Tim Cook

A spokesman for Mr Pearce's expedition said another team of Royal Marines had left Camp 5 on Thursday and climbed up to meet the two casualties to bring them down safely.

Describing the situation as "perilous", Major Tim Cook said there was "no way" they could get a helicopter up to the men because the air was so thin at that altitude.

Instead the team must first return to Camp 5 where the casualties would receive medical treatment before being stretchered down a further 8,000 feet (2,438 meters) through "treacherous terrain" to safety at Base Camp.

'Efforts concentrated'

The dangerous descent is expected to take at least four days.

Major Cook said: "It is now critical that we get those two men down to Camp 5 as quickly as possible.

"They are currently at death zone - above 26,000 feet - where the body starts to deteriorate because of the lack of oxygen.

"All our efforts are now concentrated on bringing them down safely."

Speaking from the top of the mountain before the rescue started, Mr Pearce said: "This is great for the team. It's been a hoofing team effort.

"I am thinking of all our wives, girlfriends, and family who have helped us in this endeavour."