Angry red mouths shouted insults in a foreign tongue. Hide shields smacked off scuta and broad spear blades flickered back and forth, searching for Roman flesh. Romulus' nostrils were filled with the black warriors' musty body odour. Quickly he killed the first man within reach, sliding his gladius under the man's sternum in one easy move. His next opponent was no harder to despatch; he practically ran on to Romulus' sword. The Nubian was dead before he'd even realised it.

On Romulus' right, Tarquinius was also dispatching warriors with ease, but to his left, the talkative legionary was struggling. Beset by two hulking Nubians, he soon took a spear through his right shoulder, which crippled him. He had no chance as one of his enemies pulled down his shield while the other stabbed him through the throat. It was the last thing the first Nubian did. Romulus lopped off his right hand, the one holding the spear, and with the backstroke opened the warrior's flesh from his groin to his shoulder. A legionary from the rank behind moved forward to fill the gap and together they killed the second warrior.

The dead were replaced immediately.

We need cavalry, thought Romulus as he fought on. Or some catapults. A different tactic to help their cause, which was growing desperate. Small numbers of legionaries had reached the triremes and were swarming aboard, but the majority remained trapped in a fight which they could not win. Panic flared in men's hearts and instinctively they moved backwards. Centurions roared at them to stand fast, and the standard-bearers shook their poles, trying to restore confidence, but it was no good. More ground was given away. Scenting blood, the enemy redoubled their efforts.

Romulus did not like it. He could see the situation unravelling fast.

'Keep moving!' cried a voice from behind him. 'Hold your formation. Take heart, comrades. Caesar is here!'