‘I will not wait, Mardonius,’ he said. ‘I want to go down to the sea, to watch my fleet destroy the last of their hopes. Have this city burned. It seems a dry place. I imagine flames will spread well enough.’

Xerxes looked at the canvas-and-wood awnings of the marketplace a couple of streets over. It was much smaller than he had realised. Its dimensions had been made larger in his imagination by the crimes of its inhabitants.

The market would certainly burn, as would streets of brick and plaster, roofs of tile and ancient wood. Xerxes smiled at the thought of embers lofting gently overhead, spreading. He wanted a great conflagration, a city on fire behind him. He wanted the Greeks to see the plume of smoke, to know their precious Athena could not be defended, that she had been plundered and overthrown and raped. It was a good thought.

‘Fetch me a brand, Mardonius,’ Xerxes said.

He was bright-eyed as the general whistled to waiting servants, never far from their master’s whims. When they understood, one of their number climbed the rock, nervous fingers working flint and steel. The fellow was skilled, scratching sparks onto a tuft held in his cupped fingers, then pressing the nascent flame to a club wrapped in oiled cloth, thick with tar. It spat and crackled as it caught, drawing the eye. The servant prostrated himself on the rock, so that dust stuck to his skin.

Mardonius followed the king down, as if Xerxes led a procession. The flame the king bore grew to a sooty ribbon, making trails in the air as the young man jumped from step to step, then halted in the street below.

The summer had been long and the city was dry. Xerxes raised the brand to a roof and the flame bit at laths of wood beneath the tiles. From each touch, it spread, forcing pale smoke out in thin streams as it took hold. Some tiles cracked in the heat, with notes that were almost musical. Xerxes laughed then, striding forward, pressing the flame to every house he passed. At the end of the street, he turned back, standing in the centre of the roadway as trails of smoke joined and rose, already breathing, already beyond any control or curb.

Mardonius had followed the king. The young man’s smile was hard to resist, the simple satisfaction at his achievement. When Xerxes tossed the burning brand to him, Mardonius snatched it up.

‘Finish what I have begun, general,’ Xerxes said. ‘I have decreed this city will not stand. It is their reward for defying my father. Burn it all! I am for the ships! I would see the fleet of Athens broken. Give thanks! I have shared this with you. This is a day you will remember for ever.’