‘The watershed from that range drains into an aquifer which opens there,’ says Nicolas. ‘You can see by the pattern of vegetation.’

‘Well, our casks are bone-dry, so a stop would suit us,’ Younghusband admits. ‘I’ll follow you down.’

The Pashtun servants gather brushwood, and shoot and butcher a wild goat while Nicolas puts up his tiny pup tent.

At nightfall, the air temperature drops to freezing. The sky is vast and moonless: a busy vault of stars streaked with the Milky Way, and Venus stands out as brightly as a pebble.

‘I left Peking in March,’ says Younghusband, his face yellow from the firelight. Sparks rise from the branches.

Everyone wants to be listened to, Nicolas thinks. He lets Younghusband tell his tale, how he crossed the Gobi by camel, how he travelled by moonlight, how he was bilked by a series of guides. At last, the Englishman is willing to admit to a few shortcomings. Younghusband is rightfully proud of his adventure. He is the first European to cross the Mustagh Pass. The vertiginous ice, which he negotiated in slippery leather footwear, without ice axes, and roped together with his native guides, reduced several of his party to gibbering wrecks. There is no denying the man’s hardiness and courage.

Nicolas feels a mixture of emotions: envy, resentment, but also kinship. He senses Younghusband likes it here for the same reasons that he does: this is a simple world. There is no ambivalence about their task; in spite of the secrecy, no murkiness. The interests of the Great Powers are at stake and both men know which side they’re on.

And this corner of the world is extraordinary for other reasons. Younghusband understands it too: the Kalmyk and the Tadzhik, the Kirghiz and the Pashtun, the Han Chinese and the Tibetan, the Buddhist and the Muslim. This is the reverse of the neatly embroidered cloth we take for reality; its loose ends and tangled skeins of thread are what we don’t see. The swirling mix of colours on its maps are like the marbled endpapers of the secret books. This is a place where stories intersect and grow muddled: stories of Europe and Asia, stories of Cathay and Hindustan; stories of Russia and the British Empire. Borders and endings are fuzzy, indistinct, sometimes incoherent. This would be a good place for a man to make a new start.

‘Have you any more of that brandy?’ asks Younghusband.

Nicolas offers him the flask. This time the Englishman drinks deeply. ‘I say!’ It’s impeccable stuff. Nicolas chose it in Paris for evenings just like this one: its taste evokes cedar and sandalwood and the consoling feeling of being locked in a cupboard of soft woollen coats. ‘The flask’s a bit of a relic,’ Younghusband continues, trying to read the inscription in the firelight. ‘My blasted eyes are going.’

‘It’s in Russian,’ Nicolas says. ‘From an old friend, General Skobelev.’