Saladin was astonished when plump old Thomas Busshe came riding down from Cordoba to see him in the camp.

‘You want to be careful, brother,’ Michael said to Thomas, laughing. ‘Fernando’s soldiers will eat that mule for you if you don’t keep an eye on it. And if the Saracens get hold of you they’ll eat you.’

Thomas glanced at him, gasping with exertion. ‘My son, in Seville they are Moors, not Saracens.’

‘Same thing.’ Michael went back to stirring the thick broth of root vegetables, rice and unidentifiable meat that bubbled slowly in the pot on the fire.

Thomas sat on the ground beside Saladin with a thump that sent dust flying up from his mule-blanket. His habit, heavy wool that was completely unsuitable for the climate, was caked with dust and mud and sweat.

‘You made a hazardous journey, brother,’ Saladin said, offering him his water cup. ‘The country is not yet subdued. And this, after all, is a siege.’

‘So I was advised. But your mother in Cordoba insisted I come to see you.’ He accepted a sip of water gratefully.

‘Why? What’s so important?’

‘Joan has had a letter,’ the monk said. ‘From Roger Bacon.’ And he produced a parchment.

It was more than a year since Bacon had successfully decoded the Incendium Dei scrap. Since then he had thrown himself into a vast and secretive project of experimental research, spending his time and energy and all the money he could get hold of on books and instruments and tables, hiring assistants and instructing savants.

‘He has been puffed up by his own success in cracking the code.’

‘That doesn’t surprise me,’ Saladin said.

‘And now he’s looking for engines that can deliver God’s fire.’

‘But the Codex is buried under the mosque.’

‘True. But he’s scoured Christendom and beyond for ideas on what might be possible. Look at what he speaks of - wagons that move without horses by means of a miraculous force, like the reaping chariots of the ancients, and machines for flight, and so on. He even says there is no doubt that such instruments were built in ancient times and are still being built today. He says he knows of a scholar who tried to build the flying machine . . .’

‘He speaks of this Aethelmaer of the legend.’

‘Perhaps. Or he may mean Ibn Firnas of Cordoba, who also built a flying machine some centuries ago.’

Saladin smiled thinly. ‘In Jerusalem I knew a man who sold flying carpets making much the same sort of promises. Well, Bacon is undoubtedly eager to keep our money flowing. Is it possible the ancients really did have such machines, Thomas? In a way it makes the Sihtric designs more plausible, if they are memories of the past, rather than dreams of the future.’