Then David heard it: a soft twang. It came from out in the darkness.

At the same moment, he saw the guard clutch his neck and reel. The rifle fell to the sand with a muffled thud. A second later, and no less quietly, the guard fell too.

David hunched down and felt his heart rate pick up and the world grow slow around him. Figures appeared at the periphery of his vision, a couple of dozen of them descending from the brows of the dunes and stealing towards the camp. They wore form-fitting black and moved in two-by-two formation, each pair swapping the lead with another pair. Their weapons, as far as he could tell, were pistols and short-stemmed crossbows, strictly not ba tech.

The first two raiders to reach the camp inspected the downed guards, then signalled the all-clear. The rest came padding in and set up a perimeter around the tent entrance. The camels made a few uneasy grumbles, but the black-clad raiders were so silent and precise in their actions that the beasts weren't unduly disturbed. Two of the raiders went into the tent and came out with one of the strongboxes. They carried it carefully between them, holding it perfectly level. Another two went in, and another. Soon all six strongboxes had been retrieved and the raiders got ready to pull out from the camp with their booty.

Then two things happened at once.

The first was that David felt the barrel of a gun being pressed against the back of his neck.

The second was that a Bedouin man emerged from the tent next door to the one where the strongboxes were kept.

The raiders froze. As did David, for a different reason.

''Stay still,'' whispered a voice behind him. ''Do not speak. Do not even breathe. Or I put a bullet in you.''

Meanwhile the Bedouin hitched up his robes and began to relieve himself on the sand. He glanced casually around him and spotted the raiders crouching by the adjacent tent. His urine trickled to a halt mid-flow, spattering onto his feet.