‘All right, all right. I’ll tell you this. The Chinese learned far more about the shape of the world than any European, thanks to us Moors, and thanks to their own expertise.

‘Do you know any navigation, cousin? To fix your position on the round earth you need to know two numbers, your latitude and longitude. Latitude tells you how far north you are of the equator. That’s easy. You just look for how high the Pole Star is; the higher in the sky, the further north you must have sailed, until it would be over your head if you sailed all the way to the north pole itself.

‘Longitude, the angular distance travelled east or west, is trickier, for the sky itself spins about the earth. The Chinese developed a method using eclipses of the moon. Such events are visible all across the world. A legion of astronomers scattered across the world, all studying the elevation of the stars at that precise moment, would be able to map the earth’s curve—’

Harry held up his hands. ‘Enough. I’m better at figuring accounts than the geometry of the stars.’

‘My point is that the Chinese know how big the world is. And they would tell you that it would be a long journey if you were to try to sail west from Lisbon, say, to China. But on the other hand,’ Abdul said thoughtfully, ‘that big Ocean Sea has plenty of room for an unknown continent or two. The Chinese never sailed far enough to find out.’

Geoffrey thought this through. ‘Then you’re saying,’ he said carefully, ‘that the prophecy of the Dove, the invasion of Europe by people from the west, could have a basis in truth.’

‘I’m saying it’s not impossible.’ Abdul looked at the two of them. ‘All this will take years to come to fruition, one way or another. The monarchs have other matters to deal with before they fund Ocean crossings. And the Engines of God need development before they kill anyone save by accident. We have time yet to deflect history’s course.’

Harry’s heart sank at that thought. ‘So we can’t be rid of this any time soon.’

‘Not yet,’ said Geoffrey grimly. ‘Be patient.’

XV

XV

AD 1488

The Derbyshire country under its lid of low cloud was a dark green mouth, damp and enclosing, and the abandoned village was a field of worn-down hummocks. Though it was not long after noon, the light already seemed to be fading. As he followed James and Grace into the village, Friar Diego Ferron, tall, thin, almost spectral, held up the hem of his expensive robe, as if trying to avoid any contact with the English mud.