The problem was the rise of the Turks. A decade after Seville fell to the Christians, the Mamluk Turks defeated the Mongols - the first significant defeat suffered by the nomads across three continents. It was a turning point for the Islamic empires. The Mamluks, rampant, marched on; within decades they had obliterated the last trace of the old crusader states. Eventually the Mamluks fell to new waves of Mongol invaders. But out of their shattered polities rose a new nation of Turks called the Ottomans, who dismembered what was left of the old East Roman domains. The last Roman emperor died fighting for Constantinople, when the old city fell in 1453. A jubilant Sultan Mehmet crowed that Rome itself was next, that soon he would be feeding his horses on oats from the high altar of Saint Peter’s. And in the year 1480, just a year ago, as if making good that promise, Mehmet had assaulted Italy.

‘Thus from Jerusalem to Rome Christendom is in retreat,’ Grace said relentlessly. ‘Only here in Spain are Christian armies taking the fight to the Muslims. Only here, under Isabel and Fernando, are Christians winning. And that,’ she said, ‘is the key to the future.’

Ferron considered. ‘But the monarchs are barely at ease on their own thrones. Their marriage united the Christian kingdoms of Spain, but they must deal with over-mighty nobles, empty coffers, a mixed population of Christians, Jews and Muslims - and, of course, the great canker of Granada, whose emir has refused to pay his proper tribute for fifteen years. The final war against Islam?’ He smiled, languid. ‘Let’s be rid of the Moors in Granada first and then we’ll see.’

Grace said urgently, ‘Friar Ferron, I accept what you say. But time is short.’

‘Tell me what you mean.’

And she told him briefly of another prophecy: her family’s legend of the Testament of Eadgyth. Of the mysterious, crucial figure known by his three titles, the Dove, the spawn of the spider, and the Christ-bearer. Of warring destinies, which must be resolved ‘in the last days’ - which might come as soon as the year 1500.

‘We have two decades, then,’ Ferron said drily. ‘Not long to conclude a war that has lasted for eight hundred years! But why do you want this, lady?’

‘This is my destiny. My family’s destiny, as we have perceived it since the days of Joan of the Outremer.’

Ferron pursed his lips. ‘And you are unmarried. No husband - no children.’

‘My life has a single purpose, friar. As I said, that has been the case since I was twenty. What need have I of children when I have the Engines of God?’

James shared a glance with Ferron, one of the few times the two of them communicated. Even Ferron looked disturbed by her intensity.