Ferron glared at Abdul and Geoffrey. 'This isn't over.' He turned away.

Geoffrey nodded. 'So the battle for the future is joined.'

'But for now,' Abdul said, 'we must concentrate on the needs of the present.' He took off his thick Moorish cloak and wrapped it around Agnes's bare shoulders.

James loved to climb into the hot, silent air over Granada, to escape the squabbles of mankind and the conundrums of morality, to ascend into the realm of birds, and clouds, and stars, and God. The clean, harsh breeze of Spain was even more conducive to supporting his flight than the soggy air over England's green hills. And in long hours of practice he had learned to coax his machine ever higher into the sky, even after the elastic energy of its launching crossbow was exhausted. The trick was to seek out rising masses of warm air, invisible fountains in an atmosphere like an ocean, that would lift him up like a leaf on a breeze.

And, that bright October day, he had never seen anything quite as extraordinary as Granada, the last Moorish kingdom, and the Christian military city drawn up before it.

The Alhambra was like a vast ship stranded in the middle of the land, like the Ark fallen on Ararat. Somewhere in that fortress poor Boabdil was holed up, perhaps the last emir al-Andalus would ever know. The city of Granada was a splash of grey around the Alhambra itself, studded with the glittering gold of mosque roofs. The air over the city was brown with smoke this morning, for Granada was swollen with refugees. And he could make out a thin black line of caravans and mule trains heading south, Muslims fleeing further towards the Strait and the welcoming lands of Africa.

As he wheeled away from the fortress James flew over Santa Fe – 'Holy Faith', the Christian city-camp set out on the plain before Granada. Within a circle of walls and ditches it was a crucifix of buildings, with a glittering pile of weapons where the crucifix's upright and crosspiece intersected. Santa Fe looked solid, centuries old, and yet it had been thrown up virtually overnight when the monarchs had brought their armies to within sight of the Alhambra. The speed of the construction had bewildered the Muslim defenders, but it was another of Fernando's ruses; the 'city' was more wood frame and cloth than stone.

So at last the war had come to Granada itself. It was now two years since the final defeat for El Zagal, the Valiant, brother of the dead emir Muley Hacen. Now there was only Boabdil, an emir so hapless that the Christians called him El Chico, the little one, and even he called himself the Unfortunate. Defeated and imprisoned more than once, he had already agreed terms of a final surrender. But his own people were revolted by the way he had rejoiced at his uncle's fall, and Boabdil had been forced to make a show of resistance. So Granada was besieged, with sixty thousand caballeros assembling at Santa Fe.

And in that long summer of siege and negotiation and simmering tension, of almost gladiatorial combat between Christian and Muslim champions, Cristobal Colon had once more been summoned to court. There would be yet another hearing of his case, here in Santa Fe, and one more chance for Grace Bigod and Diego Ferron to make their counter-case. Three years after the disaster of the burning-out of the manufactory of the Engines of God, Grace and Ferron still hoped that Colon, who clearly believed himself a man of destiny, could be seduced into leading a new army east in a final war against Islam.

And here was James, flying high in the air, ready to play his part. James's flying machine had been unharmed by the sabotage of the manufactory. So the plan was that as the latest debate over Colon's destiny reached its turning-point, the minds and souls of the court would be uplifted by the vision of a man-machine in the sky, with the cross of Christ painted bright red on its gossamer wings, suspended in the air like an image of the returned Virgin Mary, who in the last days would be seen in the sky with the moon at her feet.

James had become increasingly uneasy about the ardour of Grace and Ferron. He continued to find it difficult to reconcile a war against the Muslims with his own personal relationship with Christ, the prince of peace. They, however, both longed for the final cleansing war against Islam, to be waged with Grace's machines – and Ferron, burning with an Inquisitor's cruel moral certainty, really seemed to have come to believe in the approach of the end days.

But James banished his doubts and fears by pouring his energy and imagination into mastering his man-bird. He couldn't believe that the sheer beauty of the flying machine could be sinful, no matter for what purpose men intended to use it.

So he flew high over Santa Fe, making a circle over that shining heap of weapons. He saw a few faces turned up towards him, pale dots lifted to the sky. He was so high they would surely believe him an eagle or a buzzard, for you didn't expect to see men suspended in the air. The shock would be tremendous when James came dipping down out of the sky and all could see it was a man, not a bird, suspended by the ingenuity of the human mind, and that the cross of Christ burned on his wings. He grinned at the thought of it, and made a mental note to admit his sin of pride to his confessor.

Then he tugged at the cables that controlled his wings and ducked away, soaring over the Alhambra and heading for his landing site.

On the ground, at the heart of Santa Fe, Harry Wooler peered up at the hovering bird – if it was a bird. He hadn't forgotten what he had seen over Derbyshire, on that dramatic day of destruction three years ago. He said to Geoffrey, 'If he drops any of those eggs of fire this city of wood and cloth will burn like a hundred-year-old timber pile.'

Geoffrey Cotesford peered up, uninterested. 'One toy machine in the air won't make much difference. The boy flying that thing is a Franciscan, you know. James of Buxton, a bright lad according to his abbot. Now his head has been turned by these gadgets, by all this talk of war. As I've researched these prophecies I've discovered they have a peculiarly corrupting effect on scholars and holy men who should know better. A priest called Sihtric, who lived through the Conquest. A scholar from Oxford called Peter, who was burned to death during the siege of Seville. And now this James. A waste of good brains, a steady seducing of souls away from God's true purpose…'

They were walking down a broad street of trampled earth. This was a military camp, and in the low buildings around them the soldiers did what soldiers always did: ate, slept, wrestled, picked their feet, and complained about the food. There was a surprising number of Muslims here, talking to Christian officers in tight, tense groups. Even while the siege of Granada continued, Boabdil's court was in negotiation with the Christian monarchs about the terms of his almost inevitable capitulation.

And Geoffrey spoke of Cristobal Colon.

'Since the destruction of the manufactory, that day when Bartolomeo Colon was driven away from England with the stink of smoke in his nostrils, we have been winning the argument. Now we are approaching the culmination of years of work, Harry. Cristobal Colon has a thorough and well-worked-out case for his journey to the west.'

Harry said gloomily, 'But Colon has plenty of enemies at court, who think he's an obsessive buffoon, and sometimes it's hard not to agree with them. And after all these years he's growing sick of Spain. He thinks he's being strung along. It's said he's planning to approach the King of France next.'