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.