For those of an adventurous disposition, tackling the Everest Marathon is the ultimate challenge. And, as chief medical officer, it’s my job to ensure that every participant gets to realise their dream — and lives to tell the tale. 

The biennial race, which has raised more than ￡600,000 for Nepalese charities since it began in 1987, is recognised by Guinness World Records as the highest marathon in the world. The starting point is Gorak Shep, a frozen, sand-covered lake bed in Nepal, at an altitude of 17,010ft. At that height the views are sublime. However, the rarefied air provides just 50 per cent of the oxygen available at sea level. Those who fail to adapt properly will be in serious trouble, and could perish on the mountain if untreated. 

My five-strong medical team and I — all volunteers, though subsidised by the race organisers — have a duty to make sure the 80 or so runners are sufficiently acclimatised and in good health at the start line. The course undulates but it is mostly downhill. We end at the Sherpa capital of Namche Bazaar, at 11,300ft, so if you are feeling all right at Gorak Shep, you will probably reach the finish line.