Abruptly, Canthus held up his hand to signal the others to stop. The faint rush of ripples washing into the reeds faded away and then all was quiet, except the faint scrape of a horse’s hoof and a brief whinny. Ajax turned and beckoned to Karim and the two of them edged up alongside Canthus.

‘This is it,’ said the spy.

‘All right then.’ Ajax drew his sword. ‘We’ll deal with the sentries. Once they’re down, the men can take care of the rest while they sleep. Clear?’

The others nodded and drew their weapons and then Ajax led the way out of the water, up through the screen of reeds. He stopped to look over the ground. The horse line was away to the right, the animals tethered to a rope tied between two palms. Two of the sentries were talking together beside the mounts while the dark shapes of their comrades were scattered a short distance away. Some of the men were snoring. Beyond them a solitary figure strolled slowly up and down. Ajax indicated him.

‘That one’s yours, Karim. Work your way round there and silence him. I’ll count to a hundred before we move on the other two.’

Karim nodded, and then went down into a crouch and moved slowly past the sleeping Romans as he crept into the shadows of a handful of date palms and disappeared from view. Ajax counted off at a measured pace and then nudged Canthus. ‘Come on.’

They eased themselves up and out of the reeds, emerging on to a rough track that ran alongside the channel. Ajax rose to his full height and started to make his way towards the sentries by the horse line. They were still talking and did not detect the new arrivals until almost the last moment. Then the first of them spun round and lowered his spear at the two figures emerging from the darkness.

‘Halt! Who goes there?’

‘Friends!’ Canthus called back.

‘Then give me the password!’

‘Up the blues,’ Canthus called back and strode on, hand clenched round his sword handle.

‘Pass, friend!’ the Roman responded.

Ajax kept up with Canthus as the two of them continued along the track. They were close now and while the cut of Canthus’s tunic was unmistakably military, Ajax did not look like a Roman soldier. The two continued to stride forward. At the last moment one of the sentries craned his neck and squinted into the shadows. ‘Who are you?’