He turned back to the Parthian and growled, 'Tell your master we will meet – once the rest of his men have retired to a safe distance.'

'Very well, my lord.'The Parthian bowed his head, and at once turned his mount round and galloped back towards his companions, before there was any chance for the governor to change the conditions of the meeting. As they watched him go Macro turned to Cato and spoke quietly.

'Thank you so very much for involving me.'

'Sorry, sir.' Cato gestured towards the mounted squadron. 'I'd, er, better find myself a horse.'

'Fine.You do that. Before you cause any more trouble.'

While Cato trotted off in the wake of the other officers, Amatius, Macro and the governor watched as the Parthians wheeled their horses round and walked them away, leaving behind the emissary, the standard-bearer and two others. Macro puffed his cheeks out.

'Any idea what they might want, sir?'

'No. Not a clue.' Longinus was silent for a moment before he continued. 'I don't understand how they got so close to the army without being spotted. Our patrols and frontier posts must be blind. Someone's going to pay for this,' he concluded sourly.

At the sound of an approaching horse the three officers glanced round as Cato rode up to them and reined in. Longinus glanced at his companions. 'Keep your eyes open. At the first sign of danger, you shout a warning and lay into the bastards. But remember, this is a truce. We only make a move if they act first. So keep your hands clear of your weapons and in full view.'

Amatius sniffed. 'Let's hope their prince tells his people to do the same.'

'Quite.' Longinus nodded, then drew a deep breath to calm his nerves. 'Better get on with it then. Let's go.'

He gently dug the heels of his calfskin boots into the flanks of his horse and urged it forward.The others followed suit and the small party of Romans warily picked their way across the open ground towards the Parthians. As he rode a short distance behind and to one side of his commander Cato had to contain the impulse to rest his hand on the pommel of his sword. Instead he gripped the reins in both hands and stiffened his back so that he might appear haughty and fearless to the Parthians. But inside his stomach was a tight knot of fear and his heart pounded in his chest. He felt contempt for himself even as he struggled to maintain his brave facade. A glance to his side revealed Macro staring intently at the Parthians, his expression curious and appraising rather than tense and fearful. Cato snatched at the crumb of comfort that his fearless friend would be more than a match for any Parthian warrior that ever lived if the enemy had planned any treachery.

The two parties of horsemen drew closer to each other, the silence and stillness of the midday broken only by the sound of horses' hooves scraping and thumping the uneven ground. Cato saw the elaborate decoration on the Parthians' bow cases and the fine quality of their robes. Their mounts were smaller than the Roman horses, and seemed to be well cared for, muscular and moving with a fluid grace. There was little to distinguish the Parthians in their accoutrements, except that the man carrying the standard had a large wicker basket hanging from his saddle. By mutual consent the two sides drew up two spears'length apart and for a moment exchanged searching stares. Then the tallest of the Parthians suddenly pulled aside his face cloth and began to speak.

The emissary listened intently and then bowed his head before turning to the Romans.

'The prince wishes you eternal good health and prosperity. For you, your emperor and all your people. He also wishes to commend you on the fine lands you have acquired on behalf of Rome. He says that he was most impressed by your lines of watchtowers and forward outposts that guard the approaches to Antioch. They presented something of a challenge for us to approach and pass through unseen.'

Longinus' lips pressed together in a thin line as he heard the last words and his free hand momentarily clenched. Then he raised it suddenly.

'That's enough of the courtesies. I take it we're not here to discuss the details of your sightseeing. Get to the point. What does the prince want?'

There was a brief exchange between the emissary and the prince before the former spoke again. 'Parthia demands that Rome desists from any attempt to spread its influence any further towards the Euphrates.'

'Rome has every right to protect her frontiers,' Longinus responded firmly.

'Ah, but your frontiers seem to have a habit of creeping forward, like thieves towards the homes of fresh victims.'

'What do you mean? We still honour the existing treaty.'

'Between Parthia and Rome, yes,' the emissary conceded. 'But what of your arrangement with Palmyra? You use her lands as your own and your soldiers march up to the very borders of Parthia.'

'King Vabathus has signed a treaty with Rome,' Longinus said evenly. The prince snorted as the words were translated for him. Then he launched into a long outburst whose ill-humour was apparent to the Romans even before the emissary attempted to speak for his master. Macro glanced at Cato and raised his eyes wearily. Cato did not respond. His friend was a professional soldier to the core, but he hated any aspect of politics or diplomacy and it was clear to Cato that Macro's presence at this tense encounter was something of a liability for the Roman side. Cato widened his eyes and did his best to shoot a warning look at his friend. Macro briefly raised a questioning eyebrow and then shrugged slightly as the emissary spoke for his master.

'Prince Metaxas says that the true intent of your treaty is a poorly kept secret. Everyone knows that it is merely a move towards annexation of Palmyra.'

'King Vabathus entered into the treaty freely enough.'

'And if the king, or a successor, was to decide that the treaty should be ended? What then?'

Longinus had already taken the bait once, and paused a moment to consider a suitable response. 'But there is no question of that happening. Palmyra and Rome are partners.'

The Parthian prince laughed harshly and stabbed his finger towards the Roman governor as he made his response.

'Partners?' the emissary translated. 'The only partners you have are Vabathus and his cronies. The great houses of Palmyran aristocracy denounce the treaty openly. There are even those in the royal palace who think the king little more than a traitor.Your treaty is a sham, and soon the king will be forced to renounce it. And if he fails to do that you can be sure that his successor will cut the chains that bind Palmyra to Rome. If Rome attempts to intervene in Palmyran affairs by force, then Parthia will do all it can to protect its neighbour from Roman aggression.'

Now it was Longinus' turn to laugh. 'Parthia the protector? That's a new one! Your desire to seize Palmyra is transparent. What makes you think the people of Palmyra will welcome Parthian intervention?'

'We have our reasons to believe they will. And we have made it known that we will protect their independence. From Rome and any other interlopers.'

'And you think they believe that? Why should they have any more faith in your good intentions than ours?'

'Because we have not sent soldiers into their lands to build fortifications that will slowly but surely become the bars of their cage.Already you have attempted to build a fort on the very banks of the Euphrates, and before long the camps of Roman armies will sprout along the banks of the river, like knives aimed at the throat of Parthia.'

Macro leaned towards Cato and whispered, 'These Parthian buggers are partial to a poetic turn of phrase, aren't they?'

'Shh!' Cato hissed as loudly as he dared. There was a pause as the Parthian emissary, Longinus and the legate of the Tenth turned to look at Macro and Cato before the emissary resumed his master's diatribe.