After Constantine’s victory over Licinius he called for Audax to join his own personal bodyguard, the scholae palatinae. ‘You saved my life once already,’ he said in Brigantian, on greeting the boy. ‘So I believe I can trust you to do it again!’

So it was that Audax followed Constantine on the next great adventure of his reign - the move to the east. Again Aurelia had been right, and decade-old rumours were proved true. The site Constantine chose was Byzantium, a minor Greek city in Asia Minor - the place where he had won his final victory over Licinius. The new city was inaugurated only two years after that victory, and after some frantic rebuilding was dedicated four years after that.

‘The new capital must be a marvellous place.’

‘Not really,’ Audax said candidly. ‘It was thrown up quickly. Some of the new buildings are pretty shoddy, and it has attracted a scruffy class of people, I can tell you. It does have a forum and a senate of its own, and a dole of free grain, just like Rome. But it isn’t Rome yet!’

‘Ah, but it will grow.’ And, Thalius thought sadly, soon the empire’s wealth would flow from the east, from trade routes to India and beyond, and nobody would care about the western provinces with their poverty and long, vulnerable land borders: it was just as Aurelia had feared. But he said none of this to Audax. ‘It is the epicentre of empire, and will be for a thousand years. And it was founded in our lifetimes, Audax. Think of that!’

The young man’s eyes shone. ‘I do miss you, Thalius. You always did fill me with a sense of wonder.’

Thalius, moved, took his arm. ‘Then we must write. That way perhaps my fancy will enrich your life as your strength and courage have always enriched mine.’

They reached, at last, a small church. One of several in Camulodunum, it was modest, a boxy building on a rectangular plan. But it was neatly built of stone reused from some expensive ruin, and a wooden cross rose up above its tiled roof.

‘Towards the end of his life, this is where Tarcho came to worship,’ Thalius said. ‘In fact this church grew out of a soldiers’ chapel - there was once a mithraeum here, I think.’

Audax seemed briefly unable to speak. Then he said gruffly, ‘And he is buried here?’

‘Inside the church. His grave isn’t marked.’

‘It’s a fitting place for a soldier.’