Xerxes walked through streets where doors hung open and every sound echoed. Beyond a few cats warming themselves on roofs, his Immortals were the only living things he could see. They stood in long, panelled coats, ringlet beards oiled to a shine, like statues themselves. The Great King loved them as his father had, like favourite children or beloved hunting dogs, both the shield and ornament of his reign. Half their number had been killed by the red-cloaked butchers of Thermopylae. His Immortals still reeled from that blow, though they had opened the pass in the end! Xerxes had chosen to mark only that final victory, keeping them as his guards, honouring them with his blessing. The five thousand who lived were survivors: battered and bruised, but stronger for having seen the last Spartans cut down. The Immortals had not broken in that pass. Yet they had believed they were unbeatable, without equal in the world. Xerxes had witnessed their shock, their disbelief. The Spartans had made them feel helpless.

Xerxes had even considered resting the regiment, taking them out of his vanguard. Their commander was a great bull of a man – Hydarnes. With his face pressed in the dirt, he had pleaded for the Immortals then, saying they needed to work, that they would fester like a bad wound if they were given too much time to think. Xerxes had agreed. Honour could not be granted. It had to be earned through sacrifice and hard service.

At the end of a street where potters’ wheels sat untended, the light changed, brighter and airier than the roads around. Xerxes entered the famous Agora marketplace. There were the statues for the ten tribes, with stone tablets to be read out loud. He did not approach them, but he imagined at least a few warned of his own approach. His pride surged at the thought.

Xerxes looked up as a hawk keened overhead, its cry perfectly clear in the still air. The bird wove huge circles over the city and Xerxes could see the head turning, looking for prey. On any normal day, such a sound would have gone unnoticed, lost in bustle and clatter. Yet here, it was as if he sat on a mountain top and all work had ceased. It was a wonder of war, he realised, something ordinary men and women would never know.

‘I swore I would stand here, Mardonius,’ Xerxes murmured. His general only nodded, sensing the king needed no response. ‘I told my father I would finish his work, that I would bring the army to this very spot. I swore I would punish them for scorning our envoys, for refusing to offer earth and water. My father gave them a dozen chances to bend the knee, and they refused every one. They chose this, not us. Even so, to be in this place …’ He shook his head in simple pleasure. Mardonius smiled as he walked. Truly, on such a day, nothing was impossible.