They moved out before sunrise. The country was flat, with nothing to obstruct visibility, but there were dry watercourses, some deep, running across their path. Each of these could offer concealment. Mindful of this, they maintained a good order of march. No more than five paces was allowed between each mule. All the horsemen kept in close attendance, except for Hairan riding ahead on point. Valens would not let them be ambushed by bandits or tent-dwellers again.

After an hour at a walk, they stopped to check their girths, smooth the saddle blankets, and adjust the loads on the mules. As they worked, the sun came up. It threw long shadows of men and beasts. The sky was a bowl of the purest blue. It was going to be a hot day.

Remounted, they increased the pace, the horses trotting, the mules going at an amble. Riding at the head of the column, Valens watched Hairan. The bright red robe that the Hatrene wore over his armour billowed in the freshening breeze. Valens noted the little swirls of dust that lifted and snaked towards them. Beyond Hairan, on the horizon, the plain lifted to a low ridge of sand-coloured hills.

They had made no great distance before they had to rein in at a steep wadi. Dismounting, they first led the horses down its crumbling bank, and up the other side, then returned for the mules. Their hooves slipping, the baggage animals jibbed and complained at this unwanted break in their routine. The men sweated and cursed and swore.

Back in the saddle, after they had resumed station, Valens took them straight back into a trot. The hills looked surprisingly near – he had not thought they had travelled so far. Yet, lacking landmarks except the Singaras away to the right, distance was hard to judge in the desert.

‘Ahead.’ Quintus pointed.

Hairan was coming back, riding fast.

Valens felt a stab of foreboding. He squinted at the incoming rider. Hairan was not holding his cloak aloft, the signal for enemy in sight. Valens scanned the landscape. It was empty, nothing living in sight, not even a bird, although the hills seemed much nearer.

Hairan disappeared as he descended into a watercourse. Waiting for him to re-emerge, Valens held up his hand to halt the column. The day had turned dull, the sky overcast and oppressive. The crest of the hills seemed to move and shift, perhaps a mirage, or some other trick of the hazy light. Quintus had dismounted to check his mount’s feet for stones. Facing the horse’s tail, the navigator lifted each of its legs in turn, holding them between his own thighs and using a knife to clean the hoof.

Hairan popped back out of the wadi and put his horse into a gallop for the final section. He was waving an arm, shouting. The sighing of the wind, and the noise of his coming, drowned the words.