Ferox chuckled. ‘Well, I suppose if we must, we must.’

They followed the engineer to the granaries. In the best traditions of the army, the shells of the two that had burned and the remnants of the third had been thoroughly demolished, leaving an odd patch of open ground in the fort. Ephippus’ wonder was in the remaining building given over to Dacian engines. Ferox had not been there for some time, and was impressed at how much more space there was. Naso and his men had done well, aided since he arrived by Ephippus, and had managed to get a fair few of the ballistae working again. The Sicilian was now standing with great pride by one of the tall cranes.

‘So that’s what it is,’ Sabinus said, voicing the words before Ferox had a chance.

‘You see it is really a lot like one of the old staff slings. A one-arm engine rather than a two-armed like all the others. Isis knows how the Dacians knew how to make it. Advice from one of the cities on the inner sea, I suppose. I really wonder who and what plans they used. As you can see, this cranks down and is held under tension of the sinew and ropes, and you can adjust the washers so that it lobs high or low. Of course, it is not easy to aim, for you have to move the whole frame and cannot pivot at all, but then the force produced…’ It was a while before Ephippus realised that his audience had ceased to follow him.

‘Apart from its historical interest, I take it there is a reason for bringing us here,’ Ferox asked as patiently as he could.

Ephippus blinked at him, mouth hanging open and giving his face a fish-like quality. ‘You told me that you wanted something that could shoot as far as the bridge. I think that this may be the answer.’ He smiled as he saw their renewed interest. ‘That is if I can get them to work. They are in a bit of a state.’

That had been ten days ago and since then they had been busy. On several nights it had taken a direct order to send the engineer to his bed, for if he was not in the workshops, he was outside measuring and surveying, or indoors with the beads of his abacus clicking back and forth and his stylus scratching away on writing tablets. One of the machines was in a dreadful state, the other only a little better, and it was soon decided to strip all that was useful from the first. Other parts had to be made, which in turn required exact measurement and more than a little guesswork for the manual was vague on many points. After a few days Sabinus took charge of a work party building a platform extending back from the rampart about twenty paces to the left of the porta praetoria, because Ephippus informed them that the machine would need to be raised up.