‘Majesty, they are a ragged crew, after so long on the march. I think, with your permission, that they should show you greatness by shedding the blood of your enemies. God smiles on us, Majesty! To be here, in the land of the Greeks, with their cities open-legged before us, ready for the plough. We stand in the shadow of your light, Majesty, and it is glorious.’

The king did not respond for a time and Mardonius subsided. An inspection would delay them for a week or more. It would take that long just to parade the men and wash the worst dust and grime from them. He prayed in silence that the king would not follow through on his threat.

‘I am … overjoyed, Mardonius, as you say,’ the king said dreamily. ‘To be here, after so long. How far is it to Athens now?’

Mardonius cleared his throat. His finger was throbbing along with his heartbeat, quite extraordinarily painful. He wanted to mop the sweat from his brow, but he did not wish to seem nervous.

‘The scouts report a range of mountains four days’ march from here. We will find the passes through, of course. I’m told Athens is three or four days of hard marching beyond.’

Xerxes sat up, his gaze sharpening.

‘So close? Truly? Have you seen sign of their armies?’

‘Only Spartan scouts, Majesty. They appear sometimes, to watch us on the march. I send out archers, but we have not yet brought one down.’

‘It does not matter,’ Xerxes said, with a wave of his hand. ‘Let them see and fear me. They scorned my messenger, my offer to accept them as vassals. Perhaps they regret that now that I have come!’

He rose to his feet and stood swaying, so that Mardonius felt a cold horror. If the king’s excesses brought him to fainting, his general could not lay hands on him, not even to catch Xerxes as he fell. Yet if he stood by and did nothing, his life would surely be forfeit. He decided to prostrate himself on the canvas floor.

There was no crash. The king chuckled, lost in imaginings.

‘Don’t hurt their scouts, Mardonius. Let them carry what news they wish of me. I want them to know, to fear. I want them to feel the earth tremble! Now, I will go back to my ship and you will go back to your men. Keep my ships in sight! We will sweep them …’ He waved in frustration, unable to find the words. Instead, he clapped both hands together, his expression suddenly vengeful, so that small white teeth showed. ‘No … we will crush them between us.’

King Leonidas stretched out as he increased the pace, feeling his limbs loosen and his old hip injury ease. At fifty, he was proud of his strength and fitness, though he was not the sort of fool who denied the effect of time on him. It still felt right to swing along the road, his red cloak fluttering. His helots bore his shield, sword and spear. They were smaller men than the Spartan king, less powerful of frame – born to a race who had been slaves as long as the histories of man. Hundreds of them trotted like hounds in his wake, carrying the battle kit of all his guard.