After Londinium Constantine proceeded towards Camulodunum. But his route took a long detour to the north, so he could visit the fen country, an enormous quilt of farmland in the east conjured out of the sea by a vast system of dykes, canals, drainage ditches and roads - all paid for by the local people and maintained by labour levies and slaves. In older countryside the farms and settlements had grown out of communities and cultivation patterns that had been here for centuries before a Roman ever visited Britain, and so they were more disorderly, ancient, stubbornly chaotic. Here, though, the new land had been a blank canvas for the Roman planners to set down the orderly patterns they preferred, and in this utterly flat, wholly manufactured landscape the roads and dykes ran arrow-straight for mile after mile. Thalius thought that this geometric fenland was the quintessence of the obsessively disciplined Roman mind.

The reclamation wasn’t perfect, however. In places Thalius saw farmers dismally scraping at soggy ground, and some farms had been abandoned to flooding altogether. If is was true that in Germany the Ocean was rising perhaps it was true here too.

During this progression one member of the imperial court deigned to join Thalius and his companions: Ulpius Cornelius. His preliminary excuse was to show Thalius a letter he had been carrying, on a folded-over slip of wood.

Thalius scanned it quickly. It was from one Claudia Brigonia Aurelia, a widow of Eburacum - and it concerned prophecies about Constantine. Thalius handed it back hastily, chilled.

Cornelius seemed to enjoy his discomfiture. ‘Aurelia’s family, it seems, has its own legends about prophecies and emperors. Was some ancestor of hers tangled up in the complicated stories you have told me?’

‘How does she know about me?’

‘Through me,’ Cornelius said smugly. ‘I’m a thorough man, Thalius. I told you I confirmed the existence of your Prophecy through hints in the archives. But in following it up I drew extensively on contacts in Britain. And it happened that I caught the attention of this lady Aurelia, and sparked her interest.’

‘“Sparked her interest”? What does that mean, Cornelius? What does she want?’

‘Why, I’ve no idea, not specifically. But, like you - and me - it seems she has concerns about the direction in which the Emperor is taking us all.’ He grinned coldly. ‘I don’t think she had ever heard of you, Thalius. And yet it seems you have another member of your conspiratorial cabal.’

As from the beginning of his dealings with Cornelius, Thalius had the feeling that events were spinning out of his control. ‘I don’t have a conspiracy, and I don’t want a cabal!’

‘Then the Emperor has nothing to fear,’ Cornelius said smoothly. ‘And nor do you.’