He had spotted two of Sorhatani's sons. Hulegu was in a young ginkgo tree over to his right, obviously unaware that the fan-shaped leaves quivered delicately with his breathing. Arik-Boke should not have worn red in a garden with few red blossoms. Yao Shu had located him almost immediately. The khan's chancellor moved through the gardens at the centre of the young hunters, always aware of them as they shifted their positions to keep him in sight. He would have enjoyed it more if he'd been able to complete the triangle with Kublai. He was the true threat.

Yao Shu walked always in balance, gripping the earth through his sandals. His hands were loose, ready to intercept whatever came at him. It was perhaps not the behaviour of a good Buddhist to take delight in his reflexes, but Yao Shu knew it would also be a lesson for the boys, a reminder that they did not yet know everything – if he could locate Kublai, the only one of them with a bow.

With the garden less than five years old, there were only a few large trees, all of them fast-growing willows and poplars. One of them stretched across the path ahead of him and Yao Shu sensed the danger in the spot when he was still far off. It was not just that it was suitable for an ambush; there was a silence about it, a lack of butterflies and movement. Yao Shu smiled. The boys had gaped at him when he suggested the game, but a man had to move to draw and shoot a bow. To get in range, they had to ambush him or reveal their presence with movement. It was not so hard to outwit the sons of Tolui.

Kublai exploded out of the bush, his right arm coming back in the classic archer's pull. Yao Shu dropped and rolled off the path. Something was wrong, he knew it even as he moved. He heard no arrow, no slap of a bowstring. Instead of rising as he had intended, he tucked in his shoulder and rolled back to his original position. Kublai was still visible, covered in leaves and grinning. There was no bow in his hands.

Yao Shu opened his mouth to speak and heard a low whistle behind him. Another man would have turned, but he dropped again, skittering off the path and into a jerking run towards the source of the sound.

Hulegu was smiling down the length of the single arrow Yao Shu had given them that sunny afternoon. The Buddhist monk skidded to a stop. The boy had fast hands, he knew. Too fast, maybe. Still, there would be a moment.

'That was clever,' Yao Shu said.

Hulegu's eyes began to crinkle as his smile broadened. Moving smoothly, without a jerk, Yao Shu stepped close and snatched the arrow off the string. Hulegu released instinctively and, for an instant, Yao Shu thought he had it completely clear. Then his hand jumped as if it had been kicked by a horse and he spun away. The string of woven hide had struck his knuckles, jerking the arrow almost out of his grip. Yao Shu's fingers ached and he hoped he had not broken one. He did not show the boy his pain as he held out the arrow, and Hulegu took it from him with a shocked expression. It had all happened in a heartbeat, almost too fast to see.

'That was good, getting Kublai to give you the bow,' Yao Shu said.

'It was his idea,' Hulegu said a little defensively. 'He said you would be watching for his green jacket and ignoring my blue.'

Hulegu held the arrow gingerly, as if he could not believe what he had just witnessed. Kublai came up beside them and touched it almost reverently.

'You took it from the string,' Kublai said. 'That's impossible.'

Yao Shu frowned at such sloppy thinking and clasped his hands behind his back. To the boys he was the picture of relaxation. The pain in his right hand was still growing. He was sure by then that he had cracked a bone, perhaps snapped it cleanly. In truth, it had been a vain move. There were a hundred ways he could have removed the threat from Hulegu as soon as he was in range. A simple nerve block to the elbow would have made him drop the bow. Yao Shu repressed a sigh. Vanity had always been his weakness.

'Speed is not everything,' he said. 'We practise slowly until you move well, until your body has been trained to react without thought, but then, when you unleash, you must move as quickly as you can. It gives you force and power. It makes you hard to block, hard even to see. The strongest enemy can be defeated with speed and you are all young and of good stock. Your grandfather was like a striking snake until the day he died. You have that in you, if you train hard.'

Hulegu and Kublai looked at each other as Arik-Boke joined them, his face flushed and cheerful. He had not seen the khan's chancellor snatch an arrow right off the string of a drawn bow.

'Return to your studies, my young lords,' Yao Shu said. 'I will leave you now to hear reports of the khan and your father.'

'And Mongke,' Hulegu said. 'He will smash our enemies, he told me.'

'And Mongke,' Yao Shu agreed with a chuckle. He was pleased to see the flicker of disappointment in their faces as they realised their time with him was over.

For a moment, Yao Shu contemplated Kublai. Genghis would have been proud of his grandsons. Mongke had grown strong, avoiding the ravages of disease and injury. He would be a warrior to trust, a general to follow. Yet it was Kublai who impressed his tutors most, whose mind leapt on an idea and tore it to pieces before it could breathe. Of course it had been Kublai who suggested the switch with the bow. It was a simple trick, but it had almost worked.

Yao Shu bowed to the young men and turned away. He smiled as he left them on the paths, hearing the whispers as Kublai and Hulegu described again what they had seen. His hand had begun to swell, Yao Shu realised. He would have to soak and bind it.

As he reached the edge of the gardens, Yao Shu repressed a groan at the sight of the men waiting for him. Almost a dozen scribes and messengers were craning for their first sight of Ogedai's chancellor, sweating in the morning sunlight. They were his senior men. In turn, they commanded many others, almost another army of ink and paper. It amused Yao Shu to think of them as his minghaan officers. Between them, they controlled the administration of a vast and expanding area, from taxes to import licences and even public works such as the new toll bridges. Ogedai's uncle Temuge had wanted the post, but the khan had given it to the Buddhist monk who had accompanied Genghis on almost all his victories and trained his brothers and sons, with varying degrees of success. Temuge had been given the libraries of Karakorum and his demands for funds were increasing. Yao Shu knew Temuge would be one of those trying to reach him that day. The chancellor had six layers of men between supplicants and himself, but Genghis' own brother could usually browbeat them into obedience.

Yao Shu reached the group and began fielding their questions, snapping answers and making the quick decisions that were the reason Ogedai had chosen him. He needed no notes or scribes to aid his memory. He had found he could retain huge amounts of information and put it all together as he needed it. It was through his work that the Mongol lands were becoming settled, though he used Chin scholars as his bureaucracy. Slowly but surely, he was bringing a civilising influence to the Mongol court. Genghis would have hated it, but then he would have hated the very idea of Karakorum. Yao Shu smiled to himself as the questions came to an end and the group went scurrying back to their work. Genghis had conquered from a horse, but a khan could not rule from a horse. Ogedai seemed to understand that, as his father would never have done.

Yao Shu entered the palace alone, walking towards his offices. More serious decisions waited for him there. The treasury was supplying armour, weapons, food and cloth to three armies and dwindling by the day because of it. Even the immense sums Genghis had amassed would not last for ever, though he had a year or two yet before the treasury ran dry of gold and silver. By then, though, the taxes would surely have increased from a trickle to a good-sized river.