‘I will rebuild for a season here. The armies I have brought will enter all the towns and cities of this Ionian league and exact punishments as I see fit. They will take men’s hands, so they cannot carry a spear or blade again. The most beautiful children will find their way to our markets. The old men and women will be thrown on the fires. I sometimes think that is a mercy in its way – to those who would have been burdened by them. You see? Even in the furnace of my anger, there can be wisdom. I am no tyrant, Xerxes. When I move, when the mountains move, it is a trembling greater than the tread of a thousand kings. You will know the same, when I am gone. All men are slaves; all kings are slaves to us.’

His son’s face lit with pleasure at the words. Xerxes reached up with his left hand and touched the fingers resting on his bare shoulder. His father’s wisdom had built an empire of such extraordinary wealth and power, it was as he said: the world bowed to him. Xerxes thought even the rain would fall at his command.

‘And what of the Greeks, father?’

‘They have gone back in their ships, like children asleep in innocence. They have butchered my garrisons, after all. They believe the work is done. They are mistaken. The work has begun! I will see them again, when I am finished here.’

The king looked over his shoulder to the ranks of his bodyguard standing in white panelled coats. The heat must have been oppressive, but they stood in perfect stillness, as if carved from stone. The general who commanded them came forward at that single glance, prostrating himself full-length and raising both hands to his eyes as he lay on the ground, as if blinded. When he rose, dust stuck to the oil of his equipment, giving him the air of a soldier on campaign rather than mere ornament. Darius thought it was a fine omen.

‘Fetch me my bow, General Datis.’

The royal weapon was unstrapped from its case and strung in instants, while the king stood with his hand outstretched. Darius accepted the weight of it, a weapon almost as tall as he was himself, though it shone with oil and sunlight on the gold bands wrapping the grips.

‘Arrow,’ Darius said.

He fitted one to the woven string and drew as easily as any man who had practised every day since childhood. The muscles on his arm, shoulder and chest grew taut and he let it fly into the distance, soaring for an age as the ground dropped away to the plains below.

‘I send this shaft as my vow,’ Xerxes heard his father murmur. ‘God, let me punish the Athenians as they deserve.’

He handed back the bow and crooked a finger to his wine slave. Though the slender young man had served the king for all his twenty years, earning authority in the golden court, he dropped to his belly without hesitation, sensing his master’s mood.