One of the great unknowns about the trip was the effects of altitude. You can't prepare for it. It affects the fit and the unfit, old and young seemingly at random.
Normally people climbing at altitude have weeks to acclimatise. On a bike you go from 2000m to over 4000m in a day.
There is a drug, Diamox, which can aid acclimatisation but it has a few side effects like throbbing and tingling fingers.
So far, with the help of Diamox, all has gone well for Deefor. Any sort of exercise leaves you short of breath of course, but the more unpleasant effects of headaches, dizziness and poor sleep haven't kicked in.
It's not over yet though, in two days we are going to Everest Base Camp at over 5500m and that could prove harder.