'Rear five men stay with me!' shouted Macro. 'Cato! Get the others along that track as fast as you can. Head for the river and go downstream. '

'Yes, sir. But what about you?' the optio called out anxiously.

'We'll be along, Optio. Now go!'

As the rest of the century ran off down the path, Macro looked round at his companions' pale faces and grinned. He thrust his sword out into the mass on the other side of his shield. 'Right, lads! Let's make this one count. They'll not forget the Second Legion in a hurry.'

As he raced down the track, Cato tried not to step on the last man's heels. Every instinct drove him to flee as fast as he could from the sounds of the fight behind. Yet he burned with shame as well, and would have turned and run back to his centurion's side were it not for Macro's express order and the responsibility he now carried for these survivors of the Sixth Century. When the sound of the fighting had grown faint, Cato shouted out an order to halt, and quickly pushed through to the front of the century. He could not trust the man in the lead to pay heed to the location of the moon in relation to the river; he might just blunder off into the marsh.

Having got his bearings, and now no longer able to hear any sound of the centurion's last stand at the clearing, Cato ordered the century to follow him at the trot. It was dangerous to run in the dark, there were too many irregularities in the path and too many twisted roots. Far better to move at a pace they could sustain for a while yet. Jangling and chinking, the legionaries wound their way along the path in the pale moonlight and Cato was relieved to find that the track grew steadily wider and followed a generally straight line – evidence that the track was now manmade and therefore led somewhere.

A distant shout from the track behind them revealed that the Britons had taken up the chase. Cato extended his stride, snatching at breaths as he pounded along. He frequently glanced back to make sure the men were still with him. All at once he thought he heard what he was searching for: the sound of water rippling along the banks of a river. Then he was sure of the sound.

'The river, lads!' he shouted, gasping hard to draw in enough breath to be heard. 'We've made the river.'

The track twisted slightly to one side and then there it was, the great Tamesis, flowing seaward and glistening with reflected moonlight. The track abruptly gave out on to a smooth expanse of mud and Cato felt it giving way beneath his feet, sucking at his boots.

'Halt! Halt!' he cried out. 'Stay on the track!'

As the century waited, gasping in the warm air, Cato poked the ground ahead with his sword tip. The blade passed into it with almost no resistance. The shouts on the track were drawing nearer and Cato looked up in terror.

'What the fuck're we going to do, Optio?' someone called out. 'They'll be on us in a minute.'

'Swim for it!' someone suggested.

'No!' Cato replied firmly. 'There's no question of swimming anywhere. It'd be useless. They'd pick us off easily.'

He was gripped by a moment of paralysing indecision, before fresh shouting from the Britons stirred him. This time the shouting came not from the track but much closer, just along the river. He scanned the river bank until he saw a man shouting and jabbing a spear at them. Two more men squelched through the mud to join him. Beyond them, not fifty paces away, was a mass of large shell shapes hauled up from the river's edge.

'There! Boats! Let's go!' Cato shouted. He dragged his foot from the mud and planted it ahead of him where it sank past the ankle and into the grip of the foul, stinking mud. The rest of the century plunged after him and, grunting with desperate exertion, struggled towards the vessels Cato had seen. The slime squelched and sucked at their legs, and the more exhausted stumbled and were almost immersed in the filth. The three Britons watched their approach, shouting out for their comrades at the top of their voices. Glancing back, Cato saw the red glow of the torch weaving towards them and dragged himself on, forcing his legs to push their way through the mud.

Then there was a shout of triumph from behind as their pursuers reached the end of the track and caught sight of their prey stuck in the river mud. Without an instant's hesitation the Britons plunged after them, the torch bearer leading the way. The flickering red glow glimmered off the slick surface of the mud and threw the wavering shadows of Romans and Britons alike far and wide. Every sinew of his heart and body strained as Cato urged himself and his men on, calling on them to hold their shields to the rear in case their pursuers had any throwing spears.

The mud became more shallow and solid underfoot as they reached the three Britons guarding the boats. Cato struggled to get a firm footing in the slippery mud and he made for the nearest of them – an old man in rough clothes and carrying only a hunting spear. He made a two-handed thrust at Cato's body and the optio swiftly parried, deflecting the tip down into the mud, allowing the impetus of the thrust to overbalance the Briton, who was then perfectly positioned for a swift strike to his back. With a deep groan as the air was forced from his lungs, the man went face down into the mud and Cato slithered over the top of him towards the two remaining guards. They were only boys, and one look at the filthy Roman mauling for them with lips unconsciously drawn back in a snarl was more than enough. Clutching their spears they turned and ran, past the ranks of boats they were supposed to protect and off into the night. For the first time Cato could see the vessels clearly; they were small, wood-framed and skin-covered, and might hold three or four men each. They looked light and flimsy, but they were now the only chance the Sixth Century had of escaping annihilation.

Cato turned round, gasping for breath, and saw that his men were emerging from the deeper mud behind him. A short distance beyond, the British warriors came on, struggling almost knee-deep through the disturbed morass left by their quarry. The torch bearer was doing his best to keep his torch held high, and the flickering glare lit up the faces of the Britons in a terrifying red glow. One of the Romans had waded into deeper mud than his comrades and was being rapidly overhauled by his pursuers.

'Slash the sides of those boats,' Cato shouted to his men. 'But save ten for US!'

The legionaries pressed past him and set about the skin sides of the nearest boats, working quickly along the river bank. Cato stepped back towards the last Roman still struggling through the river mud, now identifiable in the mix of moonlight and the glow of the torch.

'Pyrax! Hurry, man! They're right behind you.'

The veteran glanced quickly over his shoulder as he strained to pull his leg from the mud, but the suction was too great and his last reserves of energy were nearly spent. He tried once again, cursing in accompaniment to his efforts, and with a loud sucking plop the foot came free and he planted it as far ahead of him as he could, shifted his weight and tried to extract his rear foot. But the effort required to make any further progress was too much for him and he stood for a moment, an expression of dread and frustration etched on his face. His eyes met Cato's.

'Come on, Pyrax! Move!' Cato screamed at him in desperation. 'That's an order, soldier!'

Pyrax stared a moment before his face relaxed into a grim smile. 'Sorry, Optio. Guess you'll just have to put me on a charge.'

'Pyrax… '

The legionary braced himself as firmly as he could in the mud, and twisted round to face the Britons who were several feet away but struggling forward ferociously to get at him. Appalled, Cato watched from a short distance, quite helpless to intervene, as Pyrax fought his last battle, stuck in the foul-smelling mud, screaming out his defiance to the end. In the orange cast of the torch, Cato saw the first Briton swing his sword at Pyrax's head. Pyrax blocked it with his shield, before thrusting back with his own sword. But the difference in reach between the weapons meant that he could not strike his opponent.