It used to be thought that it would be physiologically impossible to climb Mount Everest with or without oxygen. In 1953 Hillary and Tenzing proved that it was possible to reach the summit with oxygen and in 1978 Messner and Habeler demonstrated it was possible without oxygen. Although Everest has not changed, we now have a better understanding of acclimatisation, improved climbing equipment, and established routes with fixed lines guiding climbers up to the summit. For those climbing with oxygen, the cylinders are much lighter.

It would therefore seem logical that climbing Everest might have become an altogether less deadly activity. However, this year the unofficial body count on Mount Everest has reached 15, the most since the disaster of 1996 when 16 people died, eight in one night following an unexpected storm. An analysis of the death rate on Mount Everest between 1980 and 2002 found it had not changed over the years, with about one death for every 10 successful ascents. A sobering statistic for anyone who reaches the summit is that you have approximately a 1 …