Ibrahim sat down, and Peter offered him orange tea. ‘I should thank you,’ he began. ‘I owe you my life.’

‘I’d have done it for anybody. It’s my job.’

‘Which you do very well, everybody says so—’

‘If you’d gone home to England you wouldn’t have been in peril in the first place.’

‘Why would I want to do that? It’s much more interesting here. You know, I believe it’s been four years since we last met. It took you a year to fall out with your mother, as I recall,’ he said drily.

‘And you’re still working on this nonsense, after all this time.’ Ibrahim reached forward and took the parchment. ‘The Engines of God.’

‘Four years isn’t long,’ Peter said. ‘Not for a project like this. You have no idea how much ground must be laid before you can take a single step.’

‘Why a fish?’

‘Pardon?’

‘Why build a boat shaped like a fish?’

‘Because that’s what the sketches say. We are still working from the Sihtric designs.’ He meant the sketches he had been able to recover from the records of Sihtric’s clerk. It had been a long time since Ibrahim had heard the archaic name of that long-dead priest. Peter went on, ‘Oh, I can make deeper guesses about why. A fish is comfortable in the water, isn’t it? Its smooth shape simply glides through that mysterious substance. Well, then, it stands to reason that if you make a boat with the same profile, it will be similarly advantaged. That’s just my guess, though. I don’t know.

‘Progress is slow, Ibrahim. Well, you saw that, before you flounced out of the project. The sketches are partial, incomplete. Many of them are scribbles that would mean far more to the clerk who made them than to us, for whom they were never intended. We have to guess at so much - sizes, weights, materials, gearing. Very often we ask the impossible of our artisans: steel cogs of unimaginable fineness and accuracy, wooden wheels of a seamless perfection. Sometimes we simply don’t have the correct materials at all. And, what’s still more difficult, we have to make guesses as to the machines’ purposes in the first place.’

Ibrahim looked at the designs again. ‘It looks as if these stick men are totally enclosed in their fish-boat.’

‘So they are. Can you see, they operate their oars and paddles through seals in the skin of the ship, which appears to be a fine metal shell. We are using beaten copper. Some of us speculate that the ship might be sealed so that it can travel not just on the surface of the water, but beneath it.’

‘How is that possible?’