‘There is the strait – and the route we will take,’ Xerxes confirmed. He ran his finger along the map as far as he could reach. The papyrus stretched the length of the table, held at the corners with lead weights taken from a box by his servants. For a time, it was as if they stood above the world as gods. He enjoyed the sensation, as well as the murmurs of fascination in the assembled captains.

He nodded to Mardonius.

‘As soon as you are through the mountains, we will turn south and keep pace with you. You’ll reach Athens while I take the fleet around the southern tip.’

‘What of their fleet?’ Artemisia asked. ‘Athens will not let us pass without challenge. They will have warships, Majesty. No man knows how many.’

Xerxes smiled in turn.

‘We have more, Artemisia. I do not fear their ships.’

The answer did not seem to reassure her, he noticed. Instead, she pointed at the range of hills Mardonius would have to cross to keep up with the fleet.

‘And these,’ she said. ‘They do not look as high as they are, not on this map. I have seen these, in my childhood, travelling with my father.’

‘You know them, truly?’ Mardonius replied before Xerxes could.

Artemisia shrugged as all the men at that table turned to her.

‘Only once, when I was a little girl. I remember them as crags … too high to climb.’ She frowned in memory. ‘I saw steam issuing from the ground in places. My father told me the name of a pass along the coast …’

‘There is a pass, then?’ Mardonius pressed. ‘One an army can go through?’ He looked pleased, even relieved.

‘Yes,’ she said. ‘The mountains are sheer, but they end just before the sea. There is a narrow beach there … rockfall and sand …’ She looked up as a word flashed into her mind. ‘Thermopylae. That was its name.’

‘I will walk it,’ Xerxes said, suddenly. ‘I will stand on Greek soil, in honour of my father.’

He saw Mardonius blink in surprise, the older man silent as he considered his response. Before any objection could be voiced, Xerxes went on.

‘The fleet has good officers in command. I have no vital role here. Mardonius tells me these mountains are the last great obstacle before the plain that leads to Plataea and Athens – the two cities that sent men to Marathon. I would rather watch them burned than remain with the fleet.’

He did not add that the thought of sleeping once more on firm ground filled him with a sort of longing that was almost pain.

Mardonius bowed his head, constrained by the cramped quarters from doing more.

‘It would be a great honour, Majesty,’ he said.

Xerxes glanced at the queen of Halicarnassus once more. Artemisia was chewing her lip as she stared at the map, lost in memory rather than her usual acid humour.

Xerxes dipped his head, pleased with a decision made.