“That’s what strikes you,” I said to Peter. “There’s nothing medieval about this area—not like the center of British cities. Everything is planned, laid out in neat curves and straight lines. The Forum looks antique, if you know what I mean. Columns and temples, very ancient Greek. But the big palaces look like the ruins of the White House. And this market looks like the ruins of Milton Keynes.”

“Except Milton Keynes won’t last so well as Roman brickwork. They didn’t have slaves to mix the concrete so well.”

“You know, in the Dark Ages they used this place as a fortress. From shopping mall to barricade.”

He nodded thoughtfully. “Decline and fall, eh? But there were a few junctions in Rome’s history where things might have turned out different.”

“Such as?”

“Such as the loss of Britain. Needn’t have happened. Britain wasn’t just some kind of border outpost. Britain was protected by the ocean—mostly anyhow—from the pressures of the barbarians, and internally it was mostly at peace. For centuries it was a key source of wheat and weapons for the troops in Gaul and Germany, and it had a reserve of troops that could have been used to reverse the setbacks in western Europe. Even after the calamities of the early fifth century—if the emperors had won Britain back, they might have stabilized the whole of the western Empire. Maybe your grannie understood some of this.”

“If she ever existed.”

“If she existed. Well, she was the daughter of a citizen, the granddaughter of a soldier. If you’re living in great times, decisive times, you know about it, even if you only glimpse a small part of it.”

“Do you think this story of Regina can be true?”

“Well, I read the book. It’s plausible. The place-names are authentic. Durnovaria is modern Dorchester, Verulamium Saint Albans, Eburacum York. Some of the detail makes sense, too. The old Celtic festival of Samhain eventually mutated into Halloween . . . Trouble is, nobody really knows much about how Roman Britain fell apart anyhow. For sure it wasn’t like the continent, where the barbarian warlords tried to keep up the old imperial structures, though with themselves on the top. In Britain we got the Saxons—it was an apocalypse, like living through a nuclear war. The history and archaeology are scratchy, ironically, precisely because of that.”

I nodded, and sipped a little more limoncello. The bottle was already getting low. “And if the Empire had survived—”

He shrugged. “Rome would have had to fight off the expansion of Islam in the seventh century, and the Mongols in the thirteenth. But its armies would have handled the Golden Horde better than its medieval successors. It could have endured. Its eastern half did.”

“No Dark Ages—”

“The one thing you get with an empire is stability. A solemn calm. Instead of which we got a noisy clash of infant nations.”