‘How about a tower?’ Dionysius had suggested.

Ephippus dismissed the idea. ‘No. We could not build one that was high enough and strong enough.’

When the machine was pronounced ready, Ferox could understand why. It was bulkier than any ballista he had ever seen, with a rectangular frame of big, squared off beams as its base. About a third of a way back from the front was a solid upright, heavily padded and with supports joining on to the front of the frame to give it more strength, and just behind it the great metal washers. Now that he had looked – and had it explained to him plenty of times – Ferox could see that this was like one side of an ordinary ballista, whether a light scorpio or one of the big stone throwers. The only difference was that this was on its side, running between the two long sides of the frame. From it sprouted the high beam to which Ephippus had fitted what for all the world was just like a giant sling. A heavy rope hooked onto a catch on the beam, allowing it to be cranked down and held by a second cross-beam near the back, turned by a big wooden windlass worked by levers. A rachet prevented this from spinning back as the levers were lifted out and moved to the next socket.

‘You really wouldn’t want that lot going off without warning,’ Naso assured him. Like many others he had taken more and more interest in the machine as the days passed.

‘Some men just like machines,’ Ferox told Claudia when she asked why so many kept wandering down to see what was happening and whether they could help. ‘Machines are straightforward and do not get mad at you.’

‘Huh!’

Eventually Ephippus tested the mechanism under a low tension and was satisfied, so that they could begin the major task of moving the monâkon to the rampart. The engineer had designed a cart with a wide, flat platform, and cranes to help lift the engine onto it, but even so fifty men were needed to haul on the ropes. ‘I wondered about fitting the thing with wheels of its own, but am worried that it might roll back when we shoot.’

Five pairs of oxen pulled the cart, and men pushed and made sure that the wheels did not bog down as the weight pushed them into the packed grit on the road surface. Sabinus sighed at the sight of the deep trails ruining the previously flat surface. ‘I guess we have another task for a work party,’ Ferox told him.

‘The men will be delighted,’ Sabinus replied with heavy sarcasm. ‘Let’s just hope this demonic device actually works.’

‘We’ll soon see.’

Ephippus had ordered that the platform end in a ramp, and had made the slope as gentle as was possible while still permitting people to pass this section of the intervallum. Ferox had refused the engineer’s eager request to knock down a couple of barrack blocks to make more room. Posts were driven deep into the rampart so that an array of blocks, ropes and pulleys could be secured, with rollers prepared to ease the catapult as it was drawn upwards.