‘You have an adventurous soul, for a scholar. And these sketches, the fragmentary plans you say you already have—’

‘I’m no engineer. But I believe they could be developed into workable designs.’ He said this with pride, and a certain longing, for it was a project he would find fascinating to pursue if he got the chance.

She clapped her hands, almost girlish. ‘Oh, how marvellous. But you’re telling me that even if I could get to Seville, even if we manage to dig up the mosque and find these plans - even if! - they will remain incomplete.’

‘Because of the fragment taken by Robert, yes. But I have some news about that too. I was able to trace this Robert, son of Orm, and the family who followed him.’

She studied him. ‘You are resourceful, aren’t you? How?’

‘It wasn’t hard. He became known as Robert the Wolf.’

She sat back. ‘Ah. One of the most notorious of the crusaders.’

‘He settled in the Kingdom of Jerusalem, which he helped to found. His family live there still. Perhaps they know something of this Fire of God.’

‘What do you suggest, Peter of Toledo?’

He shrugged. ‘Write to the head of the family in the Outremer. She is called Joan. Tell how you may be able to help each other. I have a contact in a monastery in Colchester who could put us in touch.’

She scoffed. ‘A mudejar of Cordoba writing to a Christian family in the Outremer? You really are a dreamer, aren’t you, Peter?’

‘Why not? You have two pieces of a puzzle, it seems to me, you and this Joan of the Outremer. And if you put them together it might be mutually beneficial.’

‘And you, Christian Peter, would put these marvellous weapons in the hands of a Muslim? Would you have us make these weapons and slaughter each other?’

‘The weapons may make war too dangerous to wage. Or the engines could be turned on the common enemy.’

‘The Mongols,’ Subh said. ‘Now there’s a thought. Well, don’t worry, little Archimedes. I do sense an opportunity in these engines. But I’m no al-Mansur; business is what I know. All I want is to protect my family and my own. But if I can make a little money out of this I’ll do it.’ She smiled at him. ‘You’ve done far more than I asked of you, Peter of Toledo. You’ve earned your fee.’ But he kept his face serious, and, watching him, she grew grave. ‘Ah. But you said you had something I would not wish to hear.’

‘I do.’ And, having witnessed a near-stoning that day, Peter knew how painful it was for her to learn that her ancestress Moraima was not just the daughter of a Christian, Sihtric, but the consort of another, Robert.