Romulus knew it was time to leave. In more ways than one. With Caesar dead, he owed the Republic nothing. Octavian was reputed to be the dictator's heir, but that didn't mean Romulus wanted to fight a civil war for him, or anyone else. Standing, he stared at Brutus.

The noble sensed his question. 'Her funeral will be in eight days.'

Romulus nodded once. Despite his earlier fury, he could tell that Brutus would tolerate his presence as Fabiola was buried. The noble owed him that much.

Brutus gathered his men and was gone. Having lost too much blood, the injured Thracian was left to die.

Without further ado, Romulus and his companions headed for the nearest alley. It would be easy enough to work their way past the crowd and back into the city. Tarquinius handed over his cloak. 'Best not to advertise where you've been.'

His mind spinning, Romulus donned the garment. Eight days afforded enough time to tidy up his affairs. What would he do after that? With Caesar dead, there would be no campaign to Dacia and Parthia. Yet the thought of going back to his farm was wholly unappealing. The bugle of an elephant in the nearby arena carried through the air, and suddenly Romulus knew that he could never be happy in Italy while the slightest chance of Brennus being alive remained. He caught Tarquinius' eye and saw that the haruspex had read his mind. What about Mattius, though? There was no need to break it to him immediately, thought Romulus.

'Mattius, I have another job for you.'

'What is it?'

'Go to the Mithraeum and tell Secundus what has happened,' said Romulus. 'Caesar's heir may need some muscle in the coming days.'

Mattius repeated his words perfectly; nodding determinedly, the boy turned and ran off.

Romulus watched Mattius until he was lost to sight. Great Mithras, watch over his path, he prayed. Jupiter, Optimus Maximus, keep him from harm. He'd need to see the lawyer whom Sabinus had recommended and have his will made out in favour of the boy and his mother. Romulus' heart ached that he would have to be left behind, but Parthia and Margiana were no places for a child. Here in Rome, under the guidance of Secundus, Mattius had a chance of a future – which was more than life had offered him and Fabiola.

The haruspex looked up at the banks of scudding cloud overhead. Within a few heartbeats, a smile worked its way across his scarred face. 'I am destined to travel east again,' he announced.

Romulus looked sadly at the gladiators carrying Fabiola, and then towards the temple where Caesar's body still lay. He had lost his sister and father in the space of an hour. It was a devastating blow, yet his mother had been avenged. What had happened turned Tarquinius, and Brennus, if he was still alive, into his only family. In a strange way, that set him completely free.

At a stroke, Rome had lost its position as the centre of his world.

It mattered less than Romulus thought.

'I'll come too,' he said. Author's Note No doubt many readers will be familiar with the civil war and the events which led to Caesar's death. Where possible, I have stuck to the historical record. I would feel remiss in not doing so: the rich detail of the time lends itself so well to a novel. The night battle in Alexandria and Caesar's dramatic swim to safety, holding his documents in the air, is recorded. While he had the depleted Twenty-Seventh Legion with him, not the Twenty-Eighth, I needed Romulus to be a part of a legion that was at Ruspina too (and the Twenty-Eighth was), therefore I changed the one present in Egypt. Pharnaces' soldiers are noted to have castrated Roman citizens whom they captured. Although the use of scythed chariots at Zela is accurate, we do not know the composition of the rest of the Pontic army. I have therefore used troops common to the area and the time. Typically, peltasts and thureophoroi were skirmishers, not soldiers who would have tackled legionaries head on. Given Pharnaces' troops overwhelming numerical superiority, however, I have taken the liberty of having them attack en masse. The manner of Caesar's victory was as rapid as I described.

Rome in the late Republic was not the clean and tidy city depicted in many modern films and TV programmes. Few houses had indoor sanitation. Instead most people used public toilets, or flung the contents of their 'waste' pots on open-air dung heaps. All but two main avenues were less than 3.1 m (10 ft) wide, and most were unpaved. Buildings of three, four and even five storeys would have produced a dim twilight at street level for much of the day. Unlike Imperial times, when the city quarters were somewhat divided by social class, the rich and poor in Republican Rome lived cheek by jowl with each other. Inscribing a curse upon an enemy on a lead square and offering it to a god was commonplace, as anyone who has visited the amazing Roman baths in Bath, England, will know. Dozens of the metal squares have been retrieved and translated, opening a vivid window on the past.

Contrary to popular opinion, most of Alexandria's massive library survived the night battle in the port, thanks mostly to its two sites in the city. Unfortunately, a zealous Christian mob succeeded four centuries later in razing the lot to the ground. By doing so, they destroyed the most incredible collection of information ever seen in ancient times.

To my knowledge, the Sixth Legion did not accompany Caesar back to Italy after Zela, nor were there large games in celebration so soon after his victory in Asia Minor, but the astonishing manner in which the general dealt with the mutinous legionaries is accurate. Rhinoceroses were captured and transported to Rome at that time, and were referred to as 'Ethiopian bulls'. Noxii often died by being thrown in with such creatures. It's difficult to assess how a rhino might be killed with only a spear, and my efforts in trying to find out naturally did not go far. Try typing 'kill rhino spear' into Google and not very much comes up! Even a book by a big game hunter wasn't much use. Eventually I decided to rely on my veterinary training: virtually all mammals' hearts lie behind the left elbow, so it is a place where a spear blade can be shoved in. Whether a man can actually kill a rhino in such circumstances is a moot point, of course, but I think it is possible!

Having read about the Antikythera mechanism (the box-like object which Tarquinius nearly sees in Rhodes), I felt obliged to mention it in The Road to Rome. Although it was found over a hundred years ago, its immense significance has only become apparent in the last decade, thanks in the main to an 8-ton X-ray machine which has taken images that give incredibly fine 'slice' pictures. Built in approximately 150-100 BC, possibly in the region of Syracuse, the device was able to do all the things mentioned. Remarkably, the technology to replicate its intricate gears was not rediscovered for more than 1,500 years. If the Greeks were building things like this, what else were they able to do? How incredible that the chance discovery of a sponge diver should reveal so much. We do not know where it was being transported to at the time of its loss at sea. One popular theory, which I have used, is that it had been taken from the famous Greek Stoic school on Rhodes by Caesarean troops, who were known to have plundered the region for treasures to display at his triumphs.

My account of Ruspina largely follows the historical record, including a storm scattering Caesar's fleet, his cavalrymen feeding their horses dried seaweed, Scipio's concealment of his mounted forces until the last minute, Caesar's rebuke of the signifer and his remarkable retrieval of the situation. Labienus was attacked by a veteran legionary, not a senior centurion. Marcus Petreius, who appeared in The Silver Eagle, fought at Ruspina, and was probably injured. It is my construct that this occurred during the last action of the day, and at Romulus' hands. Before Thapsus, several Caesarean cohorts were trained specifically to fight the Pompeian elephants. Remarkably, his veteran legions were so eager to close with the enemy at the outset of the encounter that they charged before being ordered to do so. One of my favourite discoveries during the research for The Road to Rome was that during this final battle in Africa, a legionary of the Fifth 'Alaudae' Legion had successfully attacked an elephant that had picked up a camp follower, forcing it to drop its victim. I felt I had to include this sequence in the novel, even though it changed what I thought might (or might not) have happened to Brennus.