They decide to skip the normal overnight stop at Camp 2 and carry on to Camp 3 because of changing weather. If they can speed up by a whole day, they may make the summit.

Back at Base Camp, Russell announces his two summit teams, and theres a surprise for Mogens Jensen when Russell Brice puts him in the slower second team, alongside 71-year-old Japanese climber Katsusuke Yanagisawa, who hopes to be the oldest person to climb Everest.

This is it. The training and the acclimatization climbs are over, the expedition leaves Base Camp and heads for the summit.

High above the rest of the team, David Tait and Phurba Tashi are within hours of the summit, but even if they make it, they're only a quarter of the way through their extraordinary challenge.