Brennus' face filled with anger.

The Etruscan raised both hands, palms extended. 'I was passing through Transalpine Gaul a while back. Heard about the Allobroges' final battle. They said that thousands of Romans had been killed.'

Pride flared in Brennus' eyes. 'What makes you think I'm an Allobroge?'

Tarquinius smiled. 'Not much. The pigtails you had till very recently. The longsword. The way you talk.'

The Gaul laughed and Romulus relaxed.

The ship's timbers creaked gently as it moved through the water.

Romulus had rarely considered how the Romans were responsible for the suffering of other peoples. Now, seeing the emotion on Brennus' face, the truth hit him hard. The dozen races of fighters in the ludus had been there only because of the Republic's belligerent tendencies. Like Tarquinius and Brennus, their tribes had been massacred for their wealth and land. Rome was a state based on war and slavery. Romulus suddenly felt ashamed of his blood.

'Some races are destined to be greater than others and they will stop at nothing to achieve it. Such are the Romans,' said Tarquinius, reading his mind. 'That doesn't make you personally responsible for their actions.'

Romulus sighed, remembering Gemellus' rants about the founding principles of the Republic having long been subverted. All that seemed to matter now was for nobles such as Pompey, Caesar and Crassus to retain power, using the blood of ordinary men and slaves to make them rich. It was a chilling realisation. Romulus swore silently that once the campaign was over, he would never again submit to the Roman system.

'What happens is pre-ordained. When it was time, Etruria fell. Now Rome's influence is growing.'

'Nothing happens by chance?' asked Romulus.

'Nothing,' answered Tarquinius confidently. 'Not even you and your sister being sold. Not this journey. Or your future.'

The hairs on Romulus' neck rose. 'How can you know about Fabiola?'

But the Etruscan was in full flow. 'And all the while, the world keeps turning. We are just swept along with it.'

'Every fool knows that the world is flat!' interjected Brennus.

'No. You know much, but the world is round, not flat. That is how we can travel around it without falling off.'

The Gaul was taken aback. 'Where does this knowledge come from?'

'I spent years of my childhood under a great master, Olenus Aesar.' Tarquinius bowed his head.

Satisfied, Brennus nodded respectfully. The secrets of druidic lore had also been taught to Ultan by his predecessor. Perhaps Tarquinius would be able to shed some light on the old man's prophecy?

'I want to learn things like that,' said Romulus eagerly.

'It will all be revealed.' The Etruscan lay down, stretching out his legs on the deck. 'Can you read and write?'

Romulus hesitated. 'No,' he admitted.

'I will teach you.'

He burned to ask more questions, but Tarquinius had turned away to gaze at the night sky. Romulus lay back on his blanket, enjoying the movement of cool air across his skin. Their new friend's revelations had been incredible. Nobody on Achilles had met either of them before today, yet Tarquinius had known about both Fabiola and the Gaul's tribe. And what had happened outside the brothel. Clearly full of mystical ability, the Etruscan could also read and write. These were rare talents.

Being taught to use a stylus would be Romulus' first step towards real freedom. His doubts about leaving Italy began to dissipate. With two friends like Brennus and Tarquinius, there could be little to worry about.

The Gaul was snoring loudly in the darkness, oblivious. The noise kept Romulus awake for some time.

'Tarquinius?' he whispered, still eager to talk.

'What is it?'

'You know where Brennus and I came from. Our backgrounds.' How I killed Caelius, he thought with a shiver.

'Much of it.'

'So tell me what you are hiding.' Though it was dark Romulus could feel the Etruscan's gaze.

'One day. Not now.'

Curiosity filled him, but there had been an air of finality to Tarquinius' response. Romulus closed his eyes and fell asleep.

Several days into the voyage, the fleet was hit by a powerful storm that sank a dozen triremes and scattered the rest far and wide. Hundreds of legionaries and sailors were drowned, but the Achilles did not suffer as much as a scratch to her timbers. Tarquinius said nothing but Brennus began looking at their new friend with awe. Used to tales of rogue soothsayers in the temples, Romulus was less sure. It was autumn, after all.

Whatever the reason for the bad weather, it was an inauspicious start to Crassus' campaign, and rumours of bad luck began to pass between the vessels. Tarquinius did not seem perturbed by these, which seemed to relieve Brennus. But nothing further occurred to worry the superstitious soldiers and Romulus soon forgot about the Etruscan's predictions.

The fleet sailed on, past hundreds of islands forming the coastline of Greece. Seaworthy enough to venture into open water for no more than two or three days, the ships stayed close to shore. The Romans' skill at land warfare did not extend to shipbuilding. Triremes were built to sail along Republican-controlled coasts, keeping the peace – the pax Romanum.

Every sunset the flotilla dropped anchor, allowing the exhausted oarsmen time to rest. Armed parties were sent ashore to fill water barrels from rivers and streams. The food was just as Brennus predicted – hard tack and sour wine. Few of the new soldiers complained. They were happy just to be fed twice daily.

On a number of occasions, Romulus saw entire beaches covered in the burnt skeletons of ship frames, evidence of the Cilicians crushed by Pompey. The ferocious pirates had preyed on shipping for decades, costing Rome a fortune in lost trade. After a short pursuit around the eastern Mediterranean, Pompey had cornered the renegades ten years previously and crushed them. It had been a hugely popular victory for him.

A few raiders had returned to the area since, but they did not dare attack the vastly superior force. One day Romulus and his companions saw a group of sleek, dangerous looking vessels in the mouth of a small inlet only a few hundred paces away. Dark-skinned men stood watching fearfully from their decks.

But there would be no battle, as Crassus' captains were under strict orders not to delay.

Brennus raised his longsword and beckoned. 'Come and fight!'

'They prey on the weak,' Tarquinius observed. 'Not a fleet with thousands of soldiers.'

'It's been too long since I had a bout!'

The Etruscan turned his gaze back to the pirates.

'There 'll be all the fighting you need very soon.' Bassius had heard the outburst and stepped in, thinking he was preventing a quarrel. 'Quieten down.'

'Yes, sir.' The Gaul's face dropped.

'Come on, Brennus.' By now, Romulus knew the tempering effect he had on his friend. 'Show me those moves you were talking about. That all right, Senior Centurion?'

Bassius knew the journey was boring two of his best soldiers. 'I want no injuries,' he said gruffly. 'Cover your weapons.'

The pair hurried to obey. Realising there was going to be some action, the recruits quickly formed a circle on the deck. Brennus and Romulus practised every morning and by now everyone had deduced that they were trained fighters. Both men had already spent time helping Bassius teach the more eager ones some basic techniques.

Brennus crouched down, scowling ferociously. 'Let's take some wind out of your sails.'

Romulus pointed at the Gaul's belly. 'Getting fat with all this lying about!'

Laughing, the big warrior raised his longsword, its lethal edge covered in leather.

Romulus moved towards him slowly, bare feet sure on the hot deck.

Watching Brennus and his young protege spar, Tarquinius smiled. It had been many years since he trusted anyone, but the pair of runaways were becoming good friends.