It was the second-highest point in the architect Anthemius’s formidable fortifications, perched atop the Seventh Hill. Byzantium had seven hills, just as Rome had seven hills. But Leo had no intention that his city would suffer its predecessor’s dismal fate.

Katāros attended His Imperial Majesty, along with a small contingent of palace guards and the fat eparch Daniel, who was in danger of melting into a puddle of sweat on the baked pavings of the parapet. A breeze was blowing off the hot plain from the west, but it brought no relief from the unrelenting swelter of the summer sun. And it carried on its breath the stink of an army.

They had been watching all morning, watching the dust cloud grow bigger and wider, watching for it to disgorge its mysteries within.

Scouts had been flying in and out of the city with reports of the Arabs’ advance north from the Hellespont. The Emperor Leo had commanded that the land be razed ahead of them. He had been ruthless, leaving not a stalk of barley standing, and ordered any of the population who wanted to save themselves into the city. They had been pouring in for days.

Meanwhile, Prince Maslama, brother of the Caliph Sulayman, rode at the head of his great army, leaving in its wake a trail of ransacked cities and burned towns all the way back to the Cilician Gates on the eastern frontier.

And now all the rumours, all the reports, all the hearsay of bloodshed and terror, had come to their point in the dust cloud hanging over the plain.

‘There, Majesty – do you see?’ said the eparch.

‘I see.’ Leo’s tone was imperturbable as always.

Sweat was streaming into Katāros’s eyes. He palmed it away and shaded his gaze. Out of the dust, he began to distinguish spear-points glinting in the sun, shields flashing many colours, banners and pennants waving in the westerly wind. Then camels and horsemen and foot soldiers in their thousands.

The host kept coming, column after column, swallowing up the road and all the land around it. ‘Siege machines, there.’ Leo pointed out the tall, ungainly contraptions being dragged by oxen. At that distance they looked like children’s toys, but many a city to the east had learned how deadly those toys could be. ‘They hurl fire and stone.’

‘Some say they hurled shit at Pergamon,’ drawled Daniel. ‘And lime-dust. Even dead animals.’

‘They can throw what they like,’ replied Leo. ‘They won’t break our walls.’