‘Nothing,’ Ajax replied calmly. ‘There’s every chance they will take us for their own.’

Karim glanced at the black robes of the eight Arabs who were riding with them. ‘Only at a distance.’

Ajax gently steered his horse to one side so that they would not pass close by, but soon saw that the enemy horsemen were making directly for them. ‘Shit.’

‘We have to do something,’ Karim urged. ‘We have to stop them raising the alarm.’

Ajax thought quickly and turned to issue his orders. ‘Have the Arabs make their bows ready. If we get the chance we’ll take them down before they can react.’

Karim nodded and reined his horse in, falling back alongside the Arabs to convey the command to their officer.

As the two parties closed on each other, Ajax tried to calculate their chances of escaping. There was still at least a mile to go before the cliffs opened out on to the desert. If the Romans reacted swiftly enough they could cut him off from the upper Nile. The three horsemen approached without any sign of wariness. Their leader raised his hand in greeting when he was no more than fifty paces away in the half light, and then harshly reined his horse in and called out.

‘Who are you?’

‘Auxiliary horse!’ Ajax called back, nudging his mount to continue advancing. He could sense the Roman’s hesitation and the hurried exchange with the other two men. Any moment they would guess the truth.

‘Karim!’ Ajax shouted. ‘Now!’

A word of command was barked and a faint hiss cut through the air as the arrows shot towards the three Romans in a shallow arc. The leader was struck in the chest, and his horse took an arrow in the neck, causing it to rear up and throw its rider. Another arrow struck one of the riders in the thigh and the other shafts went wide. The third Roman turned and instantly kicked his heels in, galloping towards the temple a few hundred paces away. His surviving comrade struggled to pull out the arrow, giving the archers time to string a second volley. This time he was struck in the chest and face and toppled from his saddle into the sand, sending up a small cloud of dust.

‘Get that one!’ Karim bellowed, pointing to the man leaning low over the neck of his mount as it galloped to safety. More arrows flew after him but the target was moving swiftly and the range lengthening. Karim drew his sword and spurred his horse forward to give chase.

‘Leave him!’ Ajax ordered. ‘It’s too late for that. We must ride!’