“Keep your minds on what you’re doing,” he bellowed. “Look down, for God’s sake! Whatever these things are, they can’t come up to the wall. And once they get close enough the priests’ weapons will destroy them!”

If the Rome-soldiers still had been in the fortress, Shef, had realized, there would have been a deep ditch at the base of the wall, which any stormer would have had to cross before trying any kind of escalade. Centuries of neglect and refuse-tipping had filled this in, had created a swelling, turf-grown mound five feet high and as many broad. A man who ran up it would still be a dozen feet below the often-patched battlements. It had not seemed dangerous to the defenders. Indeed, without their knowing it, it had become one more hindrance to the enemy.

As the siege-tower rolled up to the wall the man at the front raised a yell, the push-teams stepped up their pace to a half-trot. The machine rolled forward, met resistance from the swelling mound, shuddered to a halt. Immediately a dozen men ran forward from their positions behind the tower. Half of them held up heavy square shields to block the arrow-shower. The others carried picks and shovels. Without words they set instantly to cutting a track along the marks of the front wheels, throwing the earth aside like badgers.

Shef walked forward between the sweating push-teams and peered through the light planking across the machine’s front. Weight, that had been the problem. In essence the tower was simply a square frame eight feet wide, twelve feet long, thirty feet high, running on six cartwheels. It was unstable and unwieldy, and the whole of both lower sides were made of the heaviest beams the houses and churches of Northumbria could provide. As defense against the English bolt-throwers. They had had to save weight somewhere, and Shef had decided to skimp at the front. The wood there was only shield-thickness. As he looked out, arrows thumped into it, driving their points through. Only inches away the diggers shoveled frantically to gain the extra two feet to advance the wheels.

That was it. As he turned to call to the push-teams there was a tumult of yells behind him, and a great crash. Shef spun round, heart leaping. A bolt? One of the giant boulders? No, not so bad. Some burly Englishman on the wall had hurled down a rock, weighing fifty pounds at least. It had crashed through the shielding and bounced into the front of the machine, splintering the planks. No matter. But there was a man down, too—Eystein, lying with his leg crooked right under the left-hand wheel, gaping up at the engine towering over him.

“Hold it!” The men checked as they gathered their muscles for the final heave that would have gone straight over Eystein’s smashed leg.