Abdul lodged small spectacles on his thin nose and scanned it quickly. '"The tail of the peacock",' he read. He looked up. 'There is an old Arab myth, of the Flood-'

'I know,' said Harry. 'Or rather, Geoffrey knows. That's what he found out. He believe that al-Andalus must be the peacock's tail of the Testament.'

'So that tells me why you've come here. But why now?'

And Harry spoke of the 'last days' of the Testament's first line, and how some Christians believed that the year 1500 in the Christian calendar would mark the end of time.

Abdul looked amused at that. 'Muslim scholars rather look down on the Christian calendar. Full of errors! Our calendars and clocks are somewhat superior – the demand for the accurate timing of the calls to prayer five times a day sees to that. But I see the relevance of the date to Christian thinking.'

'When Geoffrey found out about you, he thought you may be able to help understand the prophecy, perhaps even track down the Dove.'

'So I would be an ally in al-Andalus. And,' Abdul said drily, 'I would be committed to help, given that it is my home that will surely be the target of the marvellous weapons of which you speak.'

'What do you think we should do?'

'Think it through,' said Abdul firmly. 'Always the best policy.' He scanned down the Testament. 'Some of this seems quite explicit, doesn't it? A fire consuming "our ocean" – that must be the Mare Nostrum, as the Romans called it, our ocean, the Mediterranean. "God's Engines will… flame across the lands of spices." A massive war in the east, then, if the Dove turns that way – perhaps a war with the Islamic states which control trade with the spice islands? That much is logical. But why would this Dove, if he exists, wish to travel west? To the west is only the Ocean Sea.'

'For trade,' Harry said immediately. 'Perhaps that's a bias in my own thinking. But there is money to be made out there. That's why I would go…'

For decades European navigators had been probing the Ocean Sea, seeking new trade routes. This drive was a legacy of the Mongols, whose hundred-year peace had briefly united Asia with Europe. Travellers like Marco Polo, following the new continent-spanning trade routes, brought back accounts of great eastern empires. Italian colonies on the Black Sea and the crusader cities in the Levant made a handsome profit as conduits for imports from the east, including sugar, spices and textiles, furs, pelts and hides, wax, honey, amber, metals.

'But it wasn't only wealth that came swarming into Europe along the Mongol trade routes,' Abdul put in darkly. 'The Annihilation dawned in the heart of Asia, and travelled with the traders and their ships out of the east. You can tell from the records…'

When the Mongol peace ended, the rise of Muslim empires like the Ottomans' cut off the Christian west from the rich markets of the east. Now nobody even knew if the Khans were still on their throne. In the south too Christian traders found themselves boxed in by Muslims, who controlled the spice trade from India and the far east, and whose caravans, snaking across the Sahara, were the only access to the great gold fields of west Africa.

So, in search of new trade routes, the Europeans were taking to the seas.

'It's an exciting time,' Harry said. 'You must have seen the new maps.

The ships continue to get better too. The Portuguese, for instance, are inching their way down the west coast of Africa, seeking a sea route to the African gold mines. Some say it might be possible to go all the way down the coast of Africa and find a channel east, through to the Indian Ocean and the spice islands that way. And others are already working their way out west into the Ocean Sea. They are coming to understand how the wind blows, where the great ocean currents flow.

'And we know there are new lands to be found out there. Like Madeira, which the Portuguese control. And the Canaries, which the Spanish have conquered, and they call the Fortunate Isles.'

Abdul said, 'So there are solid reasons for this Dove to turn his energies west.' He fixed Harry with a glare. 'But you haven't told me everything, have you, cousin? If the Dove goes east there will be war between Christians and Muslims – but there is always war between Christians and Muslims. What would be so terrible about this one?'

Harry sipped his pomegranate juice. And he showed Abdul the rest of the prophecy, the lines his sister had discovered scratched in the wall of her cell in York.

Harry read,

The Dragon stirs from his eastern throne,

Walks west.

The Feathered Serpent, plague-hardened,

Flies over ocean sea,

Flies east.

Serpent and Dragon, the mortal duel

And Serpent feasts on holy flesh…

'Geoffrey Cotesford believes he now understands these words, four centuries old. This is how he has interpreted them.

'The Dove is a strong man. Strong, clever, determined. He is a force, elemental, loose in our world. He must be, or else why would the prophecy speak of him? West or east, where he goes others will follow. If he goes west, he will surely lead the conquest of lands teeming with wealth and strange peoples – lands unknown to the ancients, and to our geographers, perhaps. On the other hand, if the Dove turns east, with the same energy and single-minded purpose, he will lead a ferocious war against Islam. And he will use the Engines of God to do it. That's what Geoffrey argues. It all fits together, Geoffrey says.'

'Better weapons are always an advantage,' Abdul said. 'But Muslims aren't fools. Advantages tend not to endure.'

'Yes, that's what Geoffrey says. In time the spies of Islam will acquire the secrets of the engines. And what's more, Islam and Christianity have no means of achieving peace with each other: history shows that, says Geoffrey. So the war will be unending, the destruction on both sides will be multiplied – the use of the engines won't lead to victory but to catastrophe. From London to Baghdad, Geoffrey predicts, not a stone will be left standing. The only victors will be the warlords – whether fighting in the name of Christ or Muhammad it won't matter.

'And like all warlords, like the Mongols, they will need to feed their armies on further expansion. When the destruction of their homelands is complete they will turn their attentions outside Europe, south to Africa – and east into Asia. There will be more carnage. But China, immense, populous and ancient, will survive, as it survived the Mongols.'

'I can believe it,' Abdul said. 'How many warriors could England muster? A few thousand? It's said that the Chinese emperors command an army of a million men.' He read, '"The Dragon stirs from his eastern throne, / Walks west." I think I understand.'

Harry nodded. 'Geoffrey says this means that the Chinese will pursue the broken European armies back across the continent, all the way to France, perhaps, and even England. The last remnants of Christianity and Islam alike will become vassals of the Dragon Throne.'

'And when they have taken Europe the Chinese will face the Ocean Sea themselves.' Abdul sat forward, fascinated. 'I sailed with the Chinese, under their great eunuch admirals. Will they take their turn to explore the Ocean Sea?'

'No,' said Harry firmly. 'Not according to the prophecy. Rather, the dangers of the Ocean Sea will come to haunt them…'

Even if the Dove did not sail west, other Europeans would surely try the journey, fragile ships from Portugal and Spain and England probing ever deeper beyond the curved horizon. Others, then, would fall on the shores of the western countries – not the empires of Asia, but lands unknown to Europe, said Geoffrey.

These more tentative explorations would benefit the strange empires of the west more than the Europeans. The Dove would have conquered – or at least he would have set an example of conquest and colonisation, as opposed to reasonably peaceful contact and trade. These more timid explorers would be overwhelmed. The strange oceanic kings would indulge in trade, but in time they would acquire the newcomers' weapons and ships, take them apart, learn to make their own. They would suffer from plagues brought from Europe, but not in great numbers, and the generations to come would acquire immunity.