‘If not for … you , I would have lost my own life as well. You, an Athenian.’ Xerxes jabbed the air with his hand. ‘You warned me to protect the bridge of ships. It fell to a Greek to save me.’ He began to laugh, though it might have been sobbing, it was hard to tell. ‘Can you believe it?’

Themistocles thought he was not expected to reply. He waited, looking up at intervals. The king was wildly drunk, he realised. Young men could reach a stage of ‘ecstasis’ where the world became simple and they stepped outside themselves. It seemed Xerxes had reached that point – some time before.

‘It took my father years to gather an army and a fleet to invade Greece. I tried to finish his work and I … could not. I failed. But you know what I didn’t have? What my father didn’t have?’

Themistocles looked up, his stomach clenching.

Xerxes nodded at him.

‘He didn’t have you, Themistocles. On the night you came to me, I shouted, “I have Themistocles!” – because you are the key to going back. You are the one I will make my general, who will …’ he clutched the air, his hand closing as a claw, ‘gather them under one throne and rule … as my satrap of all Greece.’

He stared down at Themistocles in triumph.

‘Will you take my hand? Will you swear on your gods to lead my armies, Themistocles? Your word … saved me once. I know you are loyal – and you know the Greeks better than anyone. You have the … cunning I need, the mind. Will you do it?’

Themistocles took a moment to prostrate himself on the ground once more. He felt the cold stone right along the length of his body. He glanced down as he rose, half-expecting to see a shimmering image there in sweat. His smile was wide and his eyes glittered in the torchlight as he replied.

‘It would be the greatest honour of my life, Majesty. I will.’

‘Swear it on your gods, Themistocles. I know you are a pious man. Swear it on those and I will embrace you as a brother.’

Themistocles laughed.

‘It is too great an honour, Majesty, but I swear service to you, fealty to the throne. I swear it on the poet, Apollo, on Ares, the god of war – and on Athena herself. I will lead the armies of Persia back to Greece.’

Xerxes came down the steps, so swiftly Themistocles feared he might fall. To his astonishment, the young king embraced him, smearing his neck with tears and wine.

‘I want to hear your plans, Themistocles,’ Xerxes said, standing back. Slowly, he kissed the Athenian on the cheeks and then the mouth.

‘I will work on it from this moment, Majesty, I swear. I will not sleep until I can return here with a campaign for you. You honour me, Majesty, more than I deserve.’