‘The bow is usually made of metal.’

‘Not here. We couldn’t cast such an immense bow, and nor could it be bent back if we did. Look here, we use laminated wood, layers pasted and nailed together. We hired boat-builders from your Viking homelands.’

‘The vizier’s pockets must be deep.’

‘And how do you load a crossbow?’

Orm grunted. ‘Depends. The old-fashioned sort, you bend over, put your foot on a stirrup, catch the bowstring in a hook on your belt, and straighten up until you’ve got the string in the lock. The newer sort you have a little hand-crank to draw back the string. You put your bolt in the groove, and press a lever to release it.’

‘The principles are just the same here. Look at this.’ Long metal screws had been built into the body of the stock. ‘These are used to draw back the string. It isn’t hard; a single man can turn that wheel, down there. Or you can use a mule. And look, see how the carriage wheels tip outward? That’s to give the base more stability. Here’s a tilting platform so you can raise the bow, and aim the flight of the bolt. And here, you see, anchors lock the crossbow to the ground and reduce recoil.’

‘And have you fired such a thing?’

‘Only in tests. We’re still refining the design. How well do your hand bows perform?’

Orm shrugged. ‘A range of two or three hundred paces. You can pierce chain mail.’

Sihtric grinned. ‘This beauty should have a range of miles. And it will pierce masonry. Thus, one of Aethelmaer’s designs, all but realised - all but ready to be deployed in war. Tell me you’re not impressed.’

Orm pursed his lips, and walked around the machine once more. ‘Yes. I’m impressed by what you’ve built. But imagine this in war. It would take a long time to load, longer to haul it around the countryside to aim it - and it could be destroyed by a single burning arrow.’

Sihtric sighed. ‘All right. But what if I told you that instead of just knocking down a bit of wall, my arbalest could deliver a bolt capable of laying waste an entire fort, even a city? A single bolt! What then?’

Orm grimaced. ‘That sounds a fever dream, and an ugly one.’

‘But Aethelmaer had such dreams, or Aethelred did. I can show them to you, sketched in the notes. Dreams of a super-weapon - Aethelmaer called it Incendium Dei, the Conflagration of God. Perhaps it is something like Greek fire - I don’t know. But the only clues he left for it are encrypted, and it remains beyond the capabilities even of the scholars of al-Andalus to decipher. Later I’ll show you the Codex itself - much study remains to be done on it. But first, come. I’ll show you how we work here.’