Suddenly the air was filled with awful motion. Like a swarm of bees, the arrows thrummed past. The two soldiers still on horseback were hit. One slumped forward in the saddle, a look of disbelief rather than pain across his features. The other screamed and twisted, hopelessly reaching for the shaft embedded between his shoulders.

‘You bastard!’ The officer drew his sword.

The man on the ground hooked his supposedly broken leg behind the officer’s leading knee, and swept him off balance.

Landing on his back, the officer’s hilt was knocked from his grasp. Dragging air back into his chest, he scrabbled for his blade. Clutching it, he hauled himself back to his feet. The impostor was also up, sword out, well balanced, but backing away towards the lip of the precipice. Behind the officer the loose horses were milling, their hooves stamping on the hard surface.

The officer spat at the man’s feet; the worst insult for a Persian. ‘Whoever is a sinner shall be cast down to Hell.’

Valens could not get a clear shot.

After they had toppled the two mounted men from their saddles, all the horses were loose. Now the beasts sidled, rolling their eyes and throwing their heads up, alarmed by the shouts of the men, the smell of blood and the nervous movements of each other. The horses were between the six concealed archers and the Persians.

‘Swords!’ Valens yelled.

This had to be done quickly. No one could get away. He dropped his bow, snatched up his shield, and set off.

Bursting through the low shrubs, he drew his sword. Behind him he could hear the others clattering down the gully.

Emerging onto the road, he startled the nearest horse. It spun around and set off back down the way it had come. Obeying the imperative of the herd, most of the others took off after. Valens jumped back as a big chestnut almost ran him down.

The horse flashed past, and, like a warrior sprung from the very rocks of the track, a Persian stood in its place.

For a frozen moment the two men stared at each other.

Valens caught a glimpse of Narses, at the edge of the road, back to the ravine. The officer leading the supply train was attacking Narses hard, unleashing a flurry of blows. Narses was standing his ground, his blade moving like lightning to block and parry.

Then the Persian in front of Valens lunged, and the world narrowed to a circumference of just the reach of a blade.

Valens got his shield across his body. The point of the sword clanged off the metal boss of the shield, ripped through the leather cover, and gouged along its wooden surface. The impact made Valens stagger a couple of paces to regain his balance.