Altitude, honestly

Leh is at 3,500 metres. Khardung La is 5,359. Pangong is 4,250 and you sleep there. These numbers are the reason our Ladakh itinerary is nine days rather than six, and it is the most common thing people ask us to cut.

We do not cut it. Acute mountain sickness is not a function of fitness — marathon runners get it and sedentary people do not — and the only reliable protection is time. Two full days in Leh before any high pass is the minimum that experience supports.

The early signs are a headache that paracetamol does not quite fix, loss of appetite, poor sleep and breathlessness doing nothing in particular. Most people get some of this on day one and it passes. What matters is that it should be getting better, not worse, on day two.

The signs that mean descend now: confusion, an unsteady walk, a cough that brings up froth, or breathlessness at rest. These are HACE and HAPE and they are emergencies. Our vehicles carry oxygen and our drivers are trained to recognise them, but the treatment is altitude, not oxygen — you go down.

Practical things that help: drink three to four litres a day, skip alcohol entirely for the first two days, eat carbohydrate even without appetite, and do not take sleeping tablets. Diamox works and is worth discussing with your doctor before you fly.

And take travel insurance that covers evacuation. A helicopter from Nubra is not a small bill, and it is the one expense on a Ladakh trip you would rather have bought and not needed.