Peak speed Climbers set Everest records but sherpas say their values are in danger

Nothing is unusual about records being broken on Mount Everest. But last week, two sets of climbers turned heads with ascents that many had thought impossible: they went straight up from sea level to the world's highest summit in less than a week.

- Hannah Ellis-Petersen Delhi Gaurav Pockharel Kathmandu

Last Wednesday, a team of four UK climbers, all former special forces, summited Everest after flying in from London just over four days earlier. The following day, Andrew Ushakov, a US-Ukrainian climber, said he had gone from New York to the top of the 8,849-metre (29,032ft) peak in under four days.

Reaching it usually requires several weeks of acclimatisation at a lower altitude, normally at Everest base camp, so the body can adjust to the lack of oxygen.

Without this acclimatisation, most climbers would quickly die in the final stages of summiting due to the thin oxygen levels above 8,000 metres in the "death zone". Altitude sickness accounts for almost as many deaths as falls and avalanches on the mountain.

But by using new methods and technologies, both the UK team and Ushakov acclimatised their bodies before even arriving on the mountain in Nepal, meaning they could skip base camp entirely.