But Tim is so determined to prove Russell wrong that he pushes himself too hard and runs out of steam halfway to the next camp. He's struggling badly and no one's in a mood to give him a second chance.

Twenty four hours behind Tim and Team 1, the second summit team, including Danish asthmatic Mogens Jensen and 71-year-old Japanese climber Katsusuke Yanagisawa, is also on its way to the summit. Mogens is still determined to summit without bottled oxygen, but Russell doesn't think he's strong enough and worries that the hugely increased risks of climbing without oxygen might prove fatal.

As Mogens and the others get ready to leave Advance Base Camp, they're confronted with yet another reminder of how dangerous climbing Everest can be. An Irish mountaineer is brought to see expedition doctor Monica Piris with excruciatingly painful snow blindness. He went blind just below the summit and it’s taken days to get him down the mountain. He never thought he’d make it back alive. "Scariest thing I did yesterday coming down from 8,300 [meters] to North Col," the climber says. "I passed a few dead bodies, rolled over a few actually because I couldn't see them."