With a light grunt, Ortorix heaved him up and as Ajax’s boot came level with his shoulder, he gritted his teeth to edge him up still further. Keeping his weight as close to the rough surface of the mud-brick wall, Ajax groped towards the parapet. Then, as his fingers found it and curled over the edge, he let Ortorix raise him a bit further before locking an arm over the wall. He felt some of it crumble away and prayed that it would hold long enough for him to get a decent purchase on it. Then he swung his leg up, scrambling over the rim and rolled on to the walkway.

At once he rose to a crouch and looked around the interior of the fort. It was constructed in a rough square. A signal tower stood opposite the gatehouse. There were several small accommodation blocks built against the walls. Like the houses of the peasants, they had simple roofs of palm fronds to provide shade while allowing the air to circulate. A cooking fire burned in one hut and the smell of roasting meat wafted on the night air as a handful of soldiers talked in the easy way that men do when danger is furthest from their minds. There were voices coming from the other blocks, and the deep regular drone of snoring close by. The sentry patrolling along the wall had just passed through the gatehouse and was moving away from Ajax. The outline of another sentry stood at the top of the tower gazing out towards the Nile.

Satisfied that he had not been detected, Ajax leaned over the wall and gestured to the men below. Ortorix heaved the first one up and Ajax caught his hands and pulled him over the wall.

‘Get over to the gatehouse. Stay out of sight.’

The man nodded and hunched down as he made his way along the walkway. Ajax turned to help the other men up and he had ten over the parapet by the time the sentry approached the corner to turn on to the same length of wall.

‘Wait,’ Ajax whispered. ‘Stay down until I come back.’

He glanced down below the parapet and saw that there was a pile of straw and a mule tethered to a post. Resting in the straw was a fat auxiliary soldier, hands folded together across his bulging tunic. The dark shape of a wine jar lay next to him. Glancing up, Ajax saw the soldier reach the corner. There was no time to look for another place of concealment and he eased himself over the side of the walkway and dropped down into the straw. It rustled briefly and the mule started with a low bray.

‘Hrrrmmm . . .’ The auxiliary stirred and smacked his lips. ‘Whatsmatter?’