On her release from the Emperor Claudius's household, Agrippina, aged twenty-four, found employment as a bookkeeper. She worked for a moneylender, a fat, pleasant man called Marcus Crassus Cerealis, whom she eventually married.

Despite her education in Gaul, Agrippina found life in Rome very strange. It wasn't just the scale and clamouring bustle of this world capital, but the small things. In Eburacum she had grown up amid big extended families, where marriages were fluid and children were the responsibility of everybody in the roundhouse, and women had much the same power as men. Now she was stuck in a set of tiny partitioned-off rooms, with Cerealis who, despite his mild nature, clearly expected her to raise him a family alone.

But this was the life she had chosen, and she stuck to it. In time she bore Cerealis two healthy girls, whom she raised in the Roman manner.

She never left Rome again, but always followed events in her native Britain.

Aulus Plautius served as Britain's first governor for four years. In that time he established a new province, Britannia, across the south-east corner of the island. The old nations became mere administrative units, civitates, within the Roman province. Camulodunum, once the capital of a Catuvellaunian empire, was made a colony of veteran troops, the first true Roman town in Britain, and renamed Colonia Claudia. The exploitation of the British began immediately, with the systematic extraction of the province's surplus agricultural wealth. There were levies of corn and labour corvees, and soon a formalised tax system was imposed.

Caratacus, remarkably, continued to lead resistance in the west for eight years. As Nectovelin had understood, he became popular among all the nations of Britain as the one man who had not given up before the Romans-even if he never actually won a battle. Agrippina was shamed that his final betrayal was at the hands of her own queen Cartimandua, who was keen to cooperate with the Romans. She saw Caratacus brought to Rome and paraded through the city. The Romans rather liked his defiance, now that he was safely defeated, and they saw in him qualities they believed they had lost. Agrippina was dismayed that Caratacus would survive in memory not for who he was but only as an element in the Romans' own story of themselves. His usefulness over, Caratacus was pardoned and pensioned off, and she never heard of him again.

As time passed, the tapestry of history was woven thread by thread. Secretary Narcissus eventually fell foul of the complicated internal politics of the imperial family. Agrippina, who had always feared the Greek might take revenge for the humiliation of that night in Camulodunum, quietly rejoiced in his fall. She was more saddened by the death of Claudius, said to have been poisoned by his manipulative new wife. She thought it was ironic that the frail Emperor had survived assassination in faraway Britain only to be murdered in his own bed by his family.

The British meanwhile chafed under the rule of their 'two kings', the governor and procurator who jointly managed the new province. When Agrippina was forty the brutal reign of Claudius's stepson Nero provoked a revolt in Britain under an Iceni woman called Boudicca, who burned retired soldiers, lawyers, tax collectors and their families in their new temples. Her name meant 'she who brings victories'-if she had been Roman she might have been called 'Victoria'. Braint had been right, Agrippina thought, that it would take a woman to give the Romans a real fight. Boudicca had no vision beyond destruction, and failed to concentrate her energies on military targets, and in the end she fell-but not before tens of thousands had died, and the Roman hold on Britain trembled, just for a moment.

After Nero the imperial succession was bloody, and a civil war broke out between rival claimants. For Agrippina it was a terrifying time, a throwback to the days of Julius Caesar when strong men backed by private armies had battled for power. Indeed the still-young empire was nearly destroyed in the process. The crisis was resolved when an old acquaintance of Agrippina's, Vespasian, came out of retirement to become the third emperor in a year. With the competence and ruthlessness he had once shown in Britain, he soon restored order in Rome.

Meanwhile under Cartimandua, who seemed to be emulating Cunobelin of the Catuvellaunians, Agrippina's people the Brigantians, still independent of Rome, grew rich on trade with the new province to the south. There was a flowering of culture, she sensed from the letters she received from home, of literacy and music and art and education. But sprawling Brigantia was only ever a loose federation, difficult to control, and when even the queen's husband Venutius grew restive, unease about Cartimandua's Roman policy penetrated even her own bedroom. In the end Cartimandua had a reckless affair with her husband's armour-bearer, and Venutius's fury ignited civil war.

The Romans, under Vespasian's strong governors, rescued Cartimandua, and then moved into Brigantia for good, pinning it down under a network of forts and roads. They established a legionary fortress in Agrippina's old birthplace of Eburacum. After that, a generation after their first landing in south-east Britain, the Romans pushed further north still, into the misty highlands of Caledonia.

Meanwhile Agrippina's family was denuded of males by all this turmoil, and lacked heirs. Aged fifty she found herself bequeathed a majority stake in the family's quarrying business. Agrippina had no interest in overseeing this herself-but Cunedda had had a son, born in Camulodunum. Through an exchange of letters she transferred her holding to him, a last gesture to a long-dead lover.

Under the solemn calm of Vespasian's rule, Agrippina watched over her growing children. She made fitful efforts to recover Nectovelin's Prophecy, which Claudius had lodged in the vault of the Sibylline oracles, but these came to nothing. And she tried, even as she turned them into strong Roman maidens, to tell her daughters something of where their blood came from. She told them long stories from her own childhood of ancestral Brigantians, who had ruled with bronze or stone, in ages when only sheep had ruled Rome's seven hills.

But her body betrayed her. A racking cough grew steadily worse, until she woke one morning to find she had been coughing up blood.

She tried to leave her business affairs in order for the benefit of her bereft, helpless husband. Her children were both in their early twenties, they had grown into proud, strong, well-educated Roman women, and she had few concerns about them. Fifty wasn't a terribly young age to die, she told her daughters. Besides she felt her years had been crowded enough for two lifetimes.

But she had one last piece of unfinished business.