And the camp was proof that the Romans were serious, that they were here to see through this great project, here to stay. Everybody was here to further his own ambition, of course, from Vespasian and himself down to the lowliest auxiliary. Even the Emperor, already wending his own slow way from Rome, was out for what he could get. But the sum of all their individual ambitions was a dream of empire.

Vespasian brought Narcissus to a tent of his own. A legionary was stationed outside, a brute of a man who seemed suspicious of Narcissus himself. The interior of the leather tent, lugged across the Ocean on the back of some other hairy soldier, was musty, and smelled vaguely of the sea. But it contained a pallet, a bowl of dried meat and fruit, pouches of water and wine, and a small oil lantern that burned fitfully. Vespasian offered Narcissus company, but the secretary declined. It would soon be dawn, and he felt he needed time for sleep and reflection.

At last alone, Narcissus loosened his tunic and lay down on the pallet. He felt tension in his body - the clenched fists, the trembling in his gut. Resorting to a mental discipline taught him in his slave days by a captive brought from beyond the Indus, he allowed his consciousness to float around his body, soothing the tension in each finger, each toe, each muscle.

He tried to focus his mind on the needs of the coming day. He had no doubt that the subjugation of Britain would take months, years perhaps. But in the morning, when Aulus Plautius’s exuberant legates refined their plans for the first stage of their campaign, he had to be sharp. These first few hours were crucial to the realisation of the Emperor’s schemes - and his own.

It was Caesar who had first brought Britain into the consciousness of the Roman world, but of course Caesar had had his own ambitions to pursue. It was a time when the mechanisms of the Republic were creaking under the pressure of Rome’s great expansion of territory, and the Roman world was torn apart by the mutual antipathy of strong men. The invasion of Britain, a place of mystery across the terrifying Ocean, would add hugely to Caesar’s lustre.

Caesar struck at Britain twice, penetrating deep inland. But his over-extended supply lines were always vulnerable. And, as every superstitious soldier in Aulus Plautius’s four legions knew very well, Caesar’s ambitions had foundered when the Ocean’s moody weather damaged his ships. After his second withdrawal, Caesar planned to return once again. But in the next campaigning season rebellions in Gaul occupied his energies, and after that he was distracted by the turmoil that overwhelmed the Republic in its final days - turmoil that cost Caesar his own life.