That had been days ago, and once again Rufus was now convinced that the primus pilus was right. Fighting was messy, whereas making something was reassuringly predictable, at least if care was taken to spot any mistake while it was easier to put right.

Rufus ran the palm of his hand across the hard-packed surface of the ramp. He could not see well in the far distance, and sensed that Caecilius had noticed it, but other than that he felt his sight was good, at least in daylight. There was a change, he was sure of it. He had brought a stick, five feet long and painted white and red in blocks to show a carefully measured 12 inches, not that he needed to use that. Instead he laid it down, stretching the rod back so that it lay flat against the surface at the bottom of the ramp. It lay flush, which meant that the angle was consistent, and given all the care he had taken to measure it at the start, he was confident that it was also correct. Crouching, he moved the long ruler up its whole length, and still it touched the surface everywhere. He did it again, and this time it would not lie flat and flush. He was right, the angle had increased, and if it kept doing that then the slope would be steeper and all the harder to raise the tower and stop it from rolling back. Rufus lay flat on the ground to make absolutely sure.

‘Lucius,’ he hissed back. ‘Come and hold this for me.’

He heard a snigger from the darkness back in the shed, before light glinted off the top of a helmet and the legionary came towards him.

‘I want you to hold the stick as it is now,’ he whispered before the man boomed out a question. ‘Keep low and hold it steady.’ The soldier did as he was told, and Rufus reached into his pouch for a compass to measure the change of angle. It was less than he had expected, a mere one degree, but then things always felt and looked worse than they were.

‘What are you doing, sir?’ Lucius asked as the centurion crawled over to the edge of the ramp.

‘Hush!’ Rufus wanted to take a look down at the side of the ramp. ‘Go back to the shelter!’ He was at the edge before he decided that it would be hard to see while lying down and easier to kneel. He pushed up and leaned out to study the timber supports. Pale faces peered back up at him, dozens of them.

‘What are you doing?’ Rufus asked, his mind so full of the issue at hand that he surprised even himself by his stupidity. He gaped. The ditch to the side of the ramp was full of armed men, sitting and waiting.

‘Alarm! Sound the alarm!’ Lucius’ powerful voice was good for something. The man stood behind Rufus, and then raised the ruler and flung it down into the mass of enemy warriors. An arrow came back, making a dull clang as it broke through a plate on his cuirass, and then a bolt from the wall flicked the top of the parapet and slammed into his back, and he fell, pushing Rufus aside and tumbling off the side of the ramp.