He had a long spear in his right hand, with a sword and kopis knife on his belt. His helmet was a weapon when he lunged with it, as was the shield his helot brought forward and settled on his left arm. He rolled his neck, feeling bones click and crunch. He was no longer a young man.

‘Give thanks to Apollo and Ares for this opportunity,’ Leonidas called over his shoulder. ‘There is no retreat from here. This is where we die.’

The Persians broke into a run, coming at him in a line sixty or eighty wide, crammed in tight in dozens of ranks behind. It seemed they meant to smash the force of Spartans and perioikoi, to fling them away with a single charge. Leonidas set his feet on the land. His land, under him. He felt his blood thrill as the Spartan front rank locked shields and raised spears. The wall of thorns. Every man of his guard was a master of his weapons, hardened by battle and training. They held that pass like an iron bar laid across it.

Sunset came early for those who stood in the shadow of the mountains by Thermopylae. Xerxes could see great bands of gold still lighting the sea beyond, illuminating ships as they struggled wearily, like fighters clinging to one another rather than fall. It was the end of another day and an unnatural gloom fell across his army as they waited to go through the pass.

He could not understand why no great cheer was going up, why his regiments weren’t surging forward. Mardonius had sent in Assyrians, then a hazarabam of Medes. Xerxes had heard the sounds of battle begin, the cries of pain and anguish over the clash of metal on metal. The hills on his right hand echoed them back at him. It was a clamour he had known from the cradle and he found it restful. Yet there had been no trumpet pealing victory, no chanting Persian voices raised in his honour.

He saw bodies floating in the sea. At first, he thought it was some carpet of waterweed or broken oars from the fleet. Then he saw the tinge of blood in the waters like a cloud around them. He rode his horse closer to the edge and saw hundreds of the dead lying like cordwood, head to head, head to feet, face down and face up. There were no red cloaks amongst them, not that he could make out. He shivered as he sat his mount, wondering how many had drifted down and down, lost to sight, to be plucked and bitten by strange creatures on the seabed.

He called his messenger, trying not to show how desperate he was for news.

‘Pass word to Mardonius. Tell him I would hear his report.’

The young man raced away and Mardonius appeared in short order. The older man looked exhausted, the bags under his eyes seeming to have grown. Xerxes let him dismount and prostrate himself, not yet sure if the man deserved praise or censure.