Leading their horses, they walked away from the mighty arbalest and through the open-air workshop. Orm glanced with interest at the tools of the carpenters and metal-workers. He had ordered several swords in the course of a long fighting life, and had come to appreciate the metalworkers’ art; casting the immense screws of the arbalest must have set them significant challenges.

On some of the tables models were set out, intricate wooden toys that looked like birds or beetles or fish. They were models made from designs even more astonishing than the great arbalest, Orm saw, engines that flew and swam and crawled. Some of them were sliced open so you could see the wooden skeleton within, and the bodies of tiny men working oars or hauling on wheels. The boy trapped in Orm’s battered warrior’s body longed to hold these gadgets, to play with them.

In one of the tents a wooden floor had been set down, a few paces across. Its surface was incised into rows, along which stones the size of fists painted black or white were lined up. Two scholars argued in rapid Arabic over a parchment. In response to their commands a boy jumped about over the board, moving stones from one row to the next. Occasionally he apparently made a mistake, and his reward was a volley of abuse, but when he got it right the scholars forgot the boy and argued over the patterns he conjured.

‘So,’ Sihtric said. ‘Any idea what this is, Orm?’

Orm shrugged. ‘Some kind of game?’

Sihtric snorted. ‘This is deadly serious. The scholars are working out the trajectories of an arbalest bolt. We are developing an aiming system, you see. And the boy with his counters on the board is figuring the numbers for the scholars as they call out the sums.’

Orm frowned. ‘I don’t see any numbers.’

‘But they are here nonetheless, represented by the beads in their columns. This is called an abacus, Orm. It’s a counting system. You can add, subtract. You can even multiply numbers together with ease.’

Orm scoffed. ‘Everybody knows you can’t figure numbers beyond nine hundred.’

‘Using this, you can go as high as you like. With such gadgets a ten-year-old Moorish child can count better than the King of England. I’m not surprised you haven’t heard of this, or of Arabic mathematics in general. Mark my words, one day everybody in Europe will be counting this way.’

‘Turning prophet again, Sihtric? Well, we won’t be around to see it, one way or another.’

‘True. But it’s this sort of learning I came here to discover, and to exploit. Ah, here we are. My copy of Aethelred’s original sketches.’ It was a well-thumbed compendium of parchments - a document Orm hadn’t seen for twenty years, since the day he had met Aethelmaer in Westminster. ‘The Engines of God . . .’

XIII

XIII