Isolde’s mother had died young, and even as a young girl she had seen how unworldly Nennius was. Respected thinker and monk he might be, famous for his friendship with the great theologian Pelagius, but there were mornings when he couldn’t put his own trousers on the right way round. In fact Isolde grew up thinking of herself as the adult in their relationship.

Isolde had briefly escaped when she married a young man called Coponius, of ancient Roman stock. But his good looks had belied a sickly nature. Only a month after Isolde found out she was pregnant he had been carried off by a nasty little plague, one of a series that had nibbled at the population of Rome in recent years. So Isolde had had no choice but to return home to her father, a widow at nineteen, and carrying a child. Nennius was not uncaring; Isolde knew her father loved her. But with his head forever filled with one dream or another - and now stuffed with his determination to make this extraordinary journey across the known world - there was no room for Isolde.

The boat landed at a place called Rutupiae, where a grim-looking fort loomed over a good natural harbour. The fort had seen better days. Its elaborate earthworks were clogged with rubbish, and the facing stones of its massive walls were crumbling away under the assault of the caustic sea breeze. In places they looked as if they had been robbed, quarried out.

Nennius was excited, for it was here, he claimed, that Roman invaders had, centuries ago, first set foot on the island. The only Roman from such incomprehensibly ancient history Isolde had ever heard of was Julius Caesar, and when it turned out not to have been him who had conquered Britain, she lost interest.

Anyhow there were no emperors here now, and the place swarmed with Saxons. Living in clusters of small wooden buildings outside the fort’s earthworks these Germans handled the sparse trade from the continent. They used this old fort, built to repel their own piratical ancestors, as a storage depot, and just as in Gaul the only tongues you heard were Germanic.

Isolde and her father found a small timber-built church set on the fort’s north-west corner. It had a pretty baptismal font, made of reused red Roman tile. They said prayers of thanks for their safe passage this far. Then they returned to the small wharf and stood together uncertainly while the trader unloaded his boat.