The men ride uphill all morning, through a narrowing defile that rises to the top of a ridge. Nicolas is the last to reach the crest. From here, a vast valley of grey rock is spread before them under the sapphire sky. In the sunlight, the ice on the distant glaciers acquires tints of blue and green. ‘It’s heaven up here,’ says Nicolas. ‘Maybe time for another pipe?’

‘Not now,’ says Walid, laughingly, admonishing Nicolas with his finger. ‘Not while you are in heaven. Only when you are suffering in hell!’ He kicks the flanks of his horse and heads over to the other guides to repeat his bon mot.

They spend midday in the bottom of the Nubra Valley, out of the sun, grateful for the shade of willows that have been pollarded for firewood. As they rest, a caravan approaches: Bactrian camels, humps waggling under the cargo of pashm they’re carrying from Ladakh to Kashmir. The greasy matted goat’s wool will undergo an alchemical transformation at the hands of the fabled weavers and become fabric of the utmost softness.

Walid helps his master to his feet to greet the traders. Nicolas is at the limits of his linguistic knowhow, but he is able to convey his predicament in gestures and a few words of Urdu and receive rough directions towards the monastery, which seems to lie somewhere over the next range.

The following morning, just after dawn, they cross into the Indus Valley. Below them, the eponymous river is a ribbon of faded grey silk flowing across the khaki earth, watering barley fields, apricots, willows and skinny poplar trees. All day they descend, with agonising slowness, until they reach the bridge of twisted willow that carries them over the water. They hug the river, following its course downstream, until a narrow entrance opens in the vast wall of the Zanskar Range.

Night is falling when they make the final ascent up the winding path to the monastery.

Walid and the other Muslim guides fall silent. They are strangers here and unsure of the reception they can expect. The lamasery building is huge and squat, like a whitewashed keep or tenement, clinging to the contours of the rocky slope.

Nicolas’s last dose of opium was two hours ago and its effects have tailed off. His leg is beginning to throb. He’d like another pipe, but Walid needs him compos mentis. None of the guides speaks the local language. Strange sounds are emanating from the monastery: singing, drumming, cymbals, the demented protestations of brass horns.