Xuan was surprised when the small group of officials did not stop at the usual branching corridors. The apartments of more important men lay beyond, and Xuan controlled the first stirring of excitement as they went further and further still. More than one door was open, as dedicated scholars and bureaucrats laboured inside, peering out at the footsteps they heard. Xuan took a grip on his hopes. They had been dashed too many times to expect his letters to have been answered at last, though he still wrote every day.

Despite his forced calm, he felt his heart beat faster as the bowing servants brought him to the door of the man who administered the examinations for almost all the posts in Hangzhou. Sung Kim had taken the name of the royal house as his own, though Xuan suspected he had been born a commoner. As one who controlled the funds Xuan was given to maintain his small household, Sung Kim had received many of his letters over the years. Not a single one had been answered.

The servants announced him and then stood back with their heads bowed. Xuan walked into the room, pleasantly surprised to see how it opened up before him. The administrator lived in luxury, amidst sculpture and art of better than average taste. Xuan smiled to himself at the thought of complimenting Sung Kim. In such a way, he could force the odious little man to make him a present of whatever he admired, but it was just a spiteful thought. His upbringing would not allow him to be rude, despite his circumstances.

While other servants trotted away to announce his arrival, Xuan wandered from one painting to another, taking care not to linger too long on each. Time was something he had in abundance and he knew Sung Kim would make him wait.

To his intense surprise, Sung Kim himself came out of the inner rooms almost immediately. Xuan inclined his head and accepted an equally brief bow from the other man. He endured the polite observances with his usual restraint, showing no sign of his mounting impatience.

At last, he was guided into the inner rooms and tea was brought for him. Xuan settled himself comfortably, waiting.

'I have extraordinary news, Son of Heaven,' Sung Kim began. He was a very old man, with white hair and wrinkled skin, but his own excitement was visible. Xuan raised an eyebrow as if his heart did not beat harder with every moment. It was all he could do to remain silent.

'The Mongol khan is dead, Son of Heaven,' Sung Kim went on.

Xuan smiled, then chuckled, confounding the older man. 'Is that all?' he said bitterly.

'I thought…I must offer my apologies, Son of Heaven. I thought the news would bring you great joy. Does it not signal the end of your time of exile?' Sung Kim shook his head in confusion and tried again. 'Your enemy is dead, your majesty. The khan has fallen.'

'I meant no offence, Sung Kim. I have outlived two Mongol khans and that is indeed welcome news.'

'Then…I do not understand. Does it not fill your heart with happiness?'

Xuan sipped the tea, which was excellent.

'You do not know them as I do,' he said. 'They will not mourn the khan. Instead, they will raise one of his sons and they will look for new enemies. One day, Sung Kim, they will come here, to this city. Perhaps I will still be a prisoner here when that time comes. Perhaps I will stare down from these very corridors as they bring their armies to the city walls.'

'Please, Son of Heaven. You are the guest of the emperor, never a prisoner. You must not say such things.'

Xuan grimaced and set his cup down gently.

'A guest can walk away when he pleases. A guest can ride without guards. Let us be honest with one another, Sung Kim.'

'I am sorry, your majesty. I had hoped to bring you joy, not sadness.'

'Be assured, you have done both today. Now, unless you wish to discuss my written requests, I will return to my rooms.'

The administrator bowed his head. 'I cannot grant your desire to see your soldiers, Son of Heaven. Such things are far beyond my small powers.'

Xuan rose from his seat. 'Very well, but when the new khan comes, they will be needed, strong and fit. You will need every man then, I think.'

It was Sung Kim's turn to smile. The city of Hangzhou was ancient and powerful. It lay far from the border with the old Chin lands. The idea of an army ever coming close enough to cause concern was amusing.

HISTORICAL NOTE

The third son of Genghis was great khan for just twelve years, from AD 1229 to 1241. At a time when the Mongols were sweeping west into Europe, Ogedai's death would be one of the crucial turning points of history. Western Europe could not have stood against them. The medieval castles there were no more daunting than walled Chin cities, and in the field, the Mongol style of fast-striking tactical warfare would have been practically unstoppable. It is no exaggeration to say the future of the West changed when Ogedai's heart failed.

We know Ogedai was still young and died only fourteen years after his father. We do not know why he built Karakorum – the son of a khan who not only despised cities, but who had spent his entire life demonstrating how weak a defence they actually were. Yet Ogedai built a city as the throne of empire. Contemporary descriptions of it do survive – for example the words of a Christian friar, William of Rubruk. The silver tree was historical fact, as was it having shamanist temples, Islamic mosques and at least one Nestorian Christian church.

It is hard to explain why Ogedai would build such a thing at all. One explanation that fits the facts is that he was a little like Cecil Rhodes, a man whose heart pain began as young as sixteen. Before a heart attack finally killed Rhodes at forty-eight, he had built an empire for himself in Africa: a man driven to leave a mark, always knowing that he had little time to do it. Ogedai may well have had the same sense of urgency.

The second question is why he might build a city so influenced by those of the Chin – cities he had often seen burn. There, the influence of Yao Shu can be seen. Though Yao Shu was a real adviser to Ogedai, the character I have rendered is in fact an amalgam of two Chinese Buddhists from the period. I have not yet finished his tale. Worried by the khan's heavy drinking, Yao Shu showed Ogedai how wine corroded an iron bottle. It is also true that Ogedai agreed to halve the number of wine cups he drank each day, only to have cups made that were twice the size. Buddhist advisers brought a sense of Chinese civilisation to the Mongol court, subtly influencing each of the khans. As a result, cities would one day open their gates to Kublai as they never would have to his grandfather. The Three Games of Men (Naadam) in Mongolia are wrestling, archery and horse racing. The Naadam festival is indeed much older than the time of Genghis, though in previous centuries it was also a chance for tribes to horse-trade, mix bloodlines, gamble and be told the future in divinations. The modern Naadam festival has women taking part in archery and the races, though not wrestling, which is still the men's sole preserve. The description of the archery wall is accurate. Shots are taken from around a hundred paces and archers compete in groups of ten, the smallest unit of Genghis' army. Each archer has four arrows, and rather than judge individual shots, they must hit a certain number of targets to succeed. It is interesting that the archery tradition is one of teams, bearing in mind the martial nature of the sport and the vital role it played in the armies of Genghis Khan.

The horse races of the festival, which take place over three days, are all endurance races. In comparison to the West, endurance was the quality that made the khan's armies mobile and again it is interesting to see how that has remained the pre-eminent quality of equine greatness, rather than a burst of speed from a horse bred and built like a greyhound.