In slow motion, Tarquinius' gaze moved to the swarthy legionary.

It only took a moment for the scribbler's words to sink in.

'Etruscan?' snarled the soldier, wheeling towards the haruspex. 'You lying bastard. Probably a Republican agent then, aren't you?'

Too late, Aristophanes realised what he'd done. His mouth opened in an 'O' of shock as Tarquinius dropped the scroll he was holding and ran for his life.

'Spy!' screamed the legionary at his comrades. 'Spy!'

Tarquinius ran as if Cerberus and all the demons in Hades were after him, but the heavily armed men in pursuit were younger and fitter than he was. Despite his small head start, he had little chance of reaching the main entrance, let alone the streets outside. He cursed the lapse of concentration that had made him speak in Latin. Dread filled him as he pounded through the gardens, drawing startled looks from the slaves tending the plants. His claim of being a scribe would not bear up to any scrutiny, so the legionaries really would take him for a spy.

His real story was too fantastical; he also had to keep his divining abilities secret. Which meant there would be only one outcome. Death, by torture. The haruspex' lips twisted with bitterness. So the return of his abilities had been a cruel joke by the gods, devised to let him know that he could do nothing further to help Romulus, whose life he had ruined.

Then, perhaps fifteen paces away, Tarquinius saw the open door in the wall. Beside it stood a terrified-looking scribe, who was beckoning frantically. If he got through it, there was the smallest chance that the portal could be closed before the legionaries saw where he'd gone.

Pumping his arms and legs until he thought his heart would burst, Tarquinius sprinted towards it.

Pontus, northern Asia Minor It was a severe offence for an ordinary soldier to shout orders, but Romulus knew that if someone didn't, he and the men all around him would die. The trio of chariots was going to smash their part of the line apart. Throwing back his head, he roared, 'Aim short! Loose pila!'

The surrounding legionaries responded to the order instantly. Doing this was better than just staring death in the eyes. Lunging over their scuta, they hurled their javelins in unison. Dozens of the wooden shafts shot forward at the enemy chariots. At almost point-blank range, it was hard to miss. Barbed metal points punched through the horses' armour, running deep into their chests, necks and backs, while others transfixed two of the drivers, throwing them backwards on to the hard ground. Staggering and bucking with pain, their injured steeds were now out of control. They had reached such a momentum, though, that they continued moving forward. Running slightly to the rear of the others, one charioteer and his team remained unhurt. Screaming at the top of his voice, he shook his traces to encourage his horses onwards.

The first two chariots collided with the closely packed Roman lines. Romulus watched in horror as the wounded steeds smashed into the shield wall nearby, still pulling their chariots with their deadly spinning blades. Some of the men directly in their path were crushed against the soldiers behind, while others were knocked down and trampled. It was the legionaries a few steps further out who suffered the worst fate, though. This was the moment when the scythed weapons played their part. Screams of terror rose as they struck, and blood sprayed everywhere as limbs were chopped off indiscriminately.

Romulus managed to drag his attention back to the last chariot. His eyes widened. It was no more than ten steps away. The horses were going to hit the soldiers two or three over from Petronius, who was on his right. Army mounts, they were trained to ride men down. Romulus' knuckles whitened on the shaft of his remaining pilum, which felt utterly useless. The scythes on this side were going to strike Petronius, and him.

Cries of terror rose from the legionaries. A few threw pila, but their shots were poorly aimed, and flew over the chariot bearing down on them. Complete panic threatened to paralyse Romulus, and he felt his gorge rise. His muscles were locked rigid. This is what it feels like to see death approaching, he thought.

'Lie down,' shouted Petronius. 'Now!'

Romulus obeyed. It was no time to worry about the men behind. Throwing his scutum forward, he flattened himself on to the stone-covered ground. Alongside, he heard Petronius doing the same. Some men copied them, while others, panicking, turned to flee. It was too late for that. Romulus cringed; the cheek piece of his helmet bit into the side of his face. The pain helped him focus. Mithras, he prayed frantically. Don't let me end my life like this: cut in two by a fucking scythed chariot. Beneath his ear, the earth was reverberating with the thunder of pounding hooves. It scared him even more.

With a terrible whirring noise, Romulus heard one and then the other set of blades go over his body. Screams of agony rang out as the legionaries to their rear took the brunt of the chariot's impact. Beside him, Petronius lay motionless, and Romulus' mouth went dry. He must be dead, he thought, sorrow filling him. Petronius has saved my life, like Brennus did – by giving his own in return. An instant later, the chariot had gone. Incredulous, Romulus twitched his fingers and toes. They were all still there and his heart leaped first with joy, and then with guilt that he was alive while Petronius was not.

Someone gave him an almighty shove. 'That should pay you back for saving my skin in Alexandria!' The horsehair crest on Petronius' helmet had been neatly cut off, but beneath it the veteran's face was grinning and unhurt.

Romulus shouted with joy. 'I was sure you were dead.'

'Fortuna might be a capricious old whore,' laughed Petronius, 'but she's in a good mood with me today.'

They looked behind them. The chariot which had just cut men apart had come to a complete halt, the depth of the Roman formation finally using up its momentum. Like starving wolves, the nearest soldiers swarmed forward, desperate to kill man and beast. The horses were cut down, stabbed in their bellies or their hamstrings cut. Their unfortunate charioteer was no coward. Instead of trying to surrender, he reached for his sword. He didn't even get to pull it out of the scabbard. Instead, four or five screaming legionaries buried their gladii in his neck and arms. As the blades were withdrawn, the charioteer's body toppled to one side. He was not finished with yet, though. Still filled with the terror of what the scythes might have done, one of the soldiers swept his sword down, decapitating his enemy. Blood sprayed all over his legs as he stooped over the head. Ripping off the helmet, he held aloft the dripping trophy and bellowed a primeval cry of rage, which was echoed by all those who saw.

The charioteer's face still bore a grimace of surprise.

Despite causing heavy casualties, the chariots had not broken apart the Roman formation. Large holes gaped where men had fallen: serious damage to the shield wall when the battle had only just commenced. Although the gaps could quickly be filled, the legionaries' relief did not last. A new sound filled their ears. It was more horses. Bitter curses rang out.

Through the back ranks, which were facing the opposite direction, Romulus and his comrades saw the Pontic cavalry. It had ridden around the Twenty-Eighth's flanks and was now about to fall on its ill-prepared rear. Even in the best of circumstances, it was almost unheard of for infantry to stop a charge by horses. At Pharsalus, specially trained legionaries had managed it, stabbing at the enemy riders' faces with their pila and panicking them into flight. The Forgotten Legion had also done it with specially forged long spears which horses would not ride on to. Neither option was available here today, and, fully aware that they had only their javelins to throw before they were ground into the dust, the soldiers at the rear cried out in fear.