Postumus had been watching him closely, and appeared relieved that Macro did not seem to be one of the sticklers for the strict letter of the law. ‘It’s simple enough. We have a regular deal with most of the caravan cartels. Just as the Nabataeans do.They get an escort from Aelana to Petra and from there to Machaeros, where there’s another way station like this. That’s the limit of Nabataean authority. They used to escort them as far as Damascus, but we handle the last stage of the job these days.They tried to undercut us, but we made it clear that this is now our turf and the Nabataeans keep clear of us. We pocket the fee and see them safely as far as the Decapolis.’

‘Not exactly by the book, is it?’

‘No. But not exactly illegal, either.’ Postumus replied. ‘We carry out our duties patrolling the frontier, and the caravan cartels get their escort. Everyone’s happy. The thing is to make sure that word of this doesn’t spread too far, or pretty soon we’ll have Cassius Longinus clamouring for a cut, and the procurator in Caesarea. So we keep it quiet.’

‘I can imagine.’

‘Of course, the only really tricky issue is when we have to deal with fresh customers. Those caravan cartels that are new to the area. Like that one.’

‘Oh? What happens then?’

‘You’ll see.’ Postumus turned towards him. ‘When they reach us, let me do the talking, sir. Chances are they’ll know some Greek but they prefer to negotiate in their lingo and I know enough to get by.’

‘All right then.’ Macro nodded. ‘I’ll follow your lead.’

The caravan emerged from the heat haze and slowly drew closer to the way station. Macro watched them from the tower, and saw that there must be at least a hundred camels, weighed down by great baskets stuffed with bales of material, jars tightly packed into straw and other less discernible goods. Towards the front of the caravan were two large ox-carts laden with stout lengths of timber.The camels came at a steady swaying pace, goaded on by the herders walking at their side, who occasionally flicked the beasts with the ends of the slender canes they carried. On either flank of the caravan rode a handful of guards: warriors swathed in dark robes, with swords and bows slung from the wooden frames of their camel saddles. They looked fierce enough, Macro decided, but there were only twelve of them, hardly sufficient to beat off a spirited attack.