'Bastard better not be dead,' the decurion grumbled as he swung himself down from the saddle. At once the two bodyguards were at his side, looming over the man whose life had been entrusted to them.

'Alive?' one muttered.

'Yes. He's breathing.'

The Greek's eyes flickered open, then he blinked them shut against the glare of the sun. 'What… what happened?' Then he slumped back, unconscious.

'Get him up!' the decurion snapped. 'Put him on his horse.'

The Praetorians heaved the Greek on his feet and slung him back into the saddle before remounting. One took the Greek's reins while the other steadied the man with a firm grasp on his shoulder.

The decurion pointed up the track. 'Get him out of here!'

As the three men spurred towards the safety of the general's camp, the decurion swung himself back on to his mount and turned towards their pursuers.

They were much closer now, no more than three hundred paces away, and fanning out into a loose chevron as they charged towards the halted escort. Light javelins were snatched from their holsters and raised overhead, ready to throw.

'Form skirmish line!' the decurion bellowed.

His men eased their snorting ponies apart and extended across the track to face their pursuers, each man drawing his shield up to cover his body while his spare hand lowered the tip of his lance towards the rapidly approaching horsemen. The decurion wished he had thought to order his men to bring javelins with them, but he had expected an uneventful day's ride to the general's camp. Now they would have to weather the volleys of light javelins before they could close to tackle this enemy hand to hand.

'Ready!' the decurion called out to his men, giving them warning of his intention to attack. 'On my order… charge!'

With savage cries and frantic urging of their mounts the auxiliaries rippled forward, quickly picking up speed as the two small lines rushed towards each other.

The enemy horsemen showed no signs of slowing as they pounded up towards the auxiliaries. For an instant the decurion was certain that they would simply smash into his men at full tilt, and he braced himself for the impact. The impulse to recoil shivered along the ranks of his men and the line slowed down.

The decurion quickly recovered his wits and bellowed to each side, 'Keep going! Keep going!'

Ahead, the individual expressions of their pursuers could be made out: intent, silent and utterly remorseless. The flowing folds of their tunics and cloaks gave no hint of any armour beneath and the decurion almost pitied them, given the one-sided nature of the imminent clash. Man to man they could not hope to prevail against the better-protected auxiliary cavalrymen, regardless of the quality of their mounts.

At the last moment, without the need for any order, the enemy suddenly jerked their horses round and rode across the face of the Roman charge. Their javelin arms swept back.

'Look out!' cried one of the decurion's men as the several javelins swept in a low trajectory towards the escort party. This was no frantic flurry of missiles – each man had carefully picked his target – and the iron javelin heads thudded home into the chests and flanks of the cavalry mounts. Only one had struck a cavalryman, taking him low in the stomach just above the saddle horn. The targeting of their horses was quite deliberate, the decurion realised at once. Some reared up, thrashing their hoofs at the wounds, while others shied to one side with shrill whinnies of terror. Riders were forced to abandon the charge as they struggled to regain control of their beasts, and two men were thrown, crashing headlong on to the dried earth of the track.

More javelins darted through the air. The decurion's mount convulsed as a dark shaft slammed into its right shoulder. Instinctively clamping his thighs tightly to the leather saddle the decurion swore at his horse as it stopped and swung its head from side to side, sparkling flecks of saliva flying into the sunlight. Around him the rest of the escort milled about in a chaos of wounded animals and unhorsed men scrabbling to get clear of the panicked beasts.

A short distance off, the enemy had exhausted their javelins and now each man drew his sword, the long-bladed spatha that was the standard issue for the cavalry of Rome. The odds had reversed and now the escort faced extinction.

'They're going to charge!' a terrified voice cried out close by the decurion. 'Run!'

'No! Stand together!' the decurion yelled, slipping off the back of his wounded mount. 'Run, and you're fucked! Close up! Close up on me.'

It was a futile order. With half his men on foot, some still dazed from their falls, and the rest struggling to control their mounts, a co-ordinated defence was impossible. It would be every man for himself. The decurion side-stepped into an open space to give himself room to wield his spear, and stared at the enemy trotting forward, swords levelled with deadly intent.

Then an order was shouted, in Latin. 'Leave them!'

The eight horsemen sheathed their blades and, with sharp tugs of the reins, they trotted round the wary circle of cavalrymen, then picked up speed and galloped down the track in the direction of the distant camp of the legions.

'Shit!' someone muttered with an explosive exhalation of relief. 'That was close. Thought they'd carve us up good and proper.'

The decurion instinctively shared the man's sentiment for a moment, before his guts turned to ice.

'The Greek… they're after the Greek.'

They'd catch him too. Despite the head start, his groggy condition would slow the Praetorians down, and long before they reached the safety of General Plautius and his army they would be overtaken and cut down.

The decurion cursed the Greek, and cursed his own bad fortune for having been charged with the man's protection. He snatched the reins of the horse belonging to the wounded soldier still struggling to draw the javelin out of his stomach.

'Get off!'

The man's face was clenched in agony and he seemed not to have heard the order, so the decurion thrust him from the saddle and swung himself up. There was a scream of agony as the wounded man thudded heavily to the ground, the shaft of the javelin snapping.

'Anyone with a horse, follow me!' the decurion shouted, wheeling his mount and spurring it after their attackers. 'Follow me!'

He leaned low, the mane of the pony flicking back against his cheek as the animal snorted and strained every sinew to obey the savage commands of its rider. The decurion glanced round and saw that four men had broken free of the others and were galloping behind him. Five against eight. Not good. But at least there would be no more javelins, and his shield and spear would give him the edge over any man armed only with a sword. So the decurion gave chase, his heart filled with a cold desire to have his revenge on these strangers, even as his mind was filled with the need to save the Greek who had brought all this upon them.

The track dropped down a gentle slope and three hundred paces ahead galloped the enemy. A third of a mile beyond them rode the Greek and his Praetorian bodyguards who were still struggling to hold the Greek up on his horse.

'Come on!' the decurion yelled over his shoulder. 'Keep up!'

The three groups of horsemen crossed the bottom of the vale and started up the opposite slope. The earlier exertion of the pursuers' mounts began to make itself apparent as the gap between them and the decurion closed. With a growing thrill of triumph he dug his heels in and shouted encouragement into the horse's ear.'Come on! Come on, girl! One last effort!'

The gap had halved by the time the enemy had crested the hill and momentarily disappeared from view. The decurion knew for certain that he and his men would catch them up before they could fall on the Greek and his Praetorians. He glanced back and his heart lifted to see his men close behind; he would not be riding into the enemy on his own.