It was not long before there was a shout in the distance and a moment later the flicker of flames as a heavy cart was consumed by wild tongues of orange and yellow. In the glow cast round the cart Cato could see horses and mules straining at their tethers as they desperately tried to escape the heat. The shrill braying and whinnying rose to a terrified pitch. He turned back to the onagers. The guards had all moved to one side to watch the fire. Beyond them a horn blasted out in the enemy camp and suddenly the dark floor of the desert teemed with figures flowing towards the blaze. One of the guards shouted, and ran a few paces towards the flames, then paused and gestured angrily for the others to follow. One shook his head and shouted back, stabbing his finger to the ground at his feet, refusing to move. But a handful of others rushed to join the first man and they ran off into the night.

Cato turned to his men. ‘Follow me. No man strikes until I say.’

Rising to a crouch, Cato ran towards the onager furthest from the remaining guards and with a soft padding of footsteps his men followed. When they reached the onager Cato took off his haversack and opened it.

‘As soon as I’ve got this one alight take down those guards. Draw your swords.’

The was a quiet chorus of rasps as the men slowly took their swords from their scabbards and held them ready. While two of them started dousing the onager’s frame and torsion ropes with oil, others found some spare rope and combustibles to place under the frame. Cato prepared some carbonised linen in his tinderbox together with some shreds of dried bark.Then he struck his flints. After the first few frustrating attempts a small shower of sparks caught on the linen and he blew softly over them until, with a tiny pop, a small lick of flame appeared. Carefully he drew some of the bark over to feed the flame and then when there was a healthy crackle he lowered it to the kindling materials. There was a maddening delay before the flames spread from the tinderbox, but at last the flames were licking up from the base of the onager and spread rapidly as the oil caught fire and bathed the surrounding area in a lurid glow.

There was a shout of alarm from the remaining guards as they turned towards the blaze.