So she lay with her head in the crook of my arm, and all the rest of her posed strategically as far from my body heat as she could arrange.

‘Alexander has discovered women,’ she said.

‘Alexander has discovered the siege of Troy,’ I said. ‘And that Helen has an identical twin sister.’

The army speculated endlessly that he was having both of them at the same time, an impractical fantasy that appealed to every Thracian, every Greek mercenary and every Macedonian – every man, and some of the women, too.

A week or so after they arrived, I entered my pavilion to find both of them sitting with Thaïs, drinking sherbet in the Persian manner. Thaïs looked beautiful, despite her pregnancy and even because of it – pregnancy enhances some things, and not just breasts – hair, and skin.

Barsines sat next to Thaïs, and Banugul closer to the door, and a pair of slaves fanned them while Bella, my love’s Libyan, brought food and wine.

I was wearing a soldier’s chiton over a naked body. I had been carrying rocks. I imagine that I smelled.

Both women rose to their feet and offered deep curtsies. I returned them – I’m a gentleman, despite being dressed as a slave.

Thaïs stayed seated. ‘My lover, the taxiarch Ptolemy,’ she said in a matter-of-fact manner.

Both women curtsied again.

Bella brought Eurydike into the tent, and Thaïs gave her a big hug and a kiss, while Eurydike looked out from the safety of her mother’s embrace at the two women. ‘Ooh!’ she said. ‘Real princesses!’ She had just begun to speak well. She was a little more than two, and she was never shy.

The two women laughed easily, and Barsines reached out for the child, who came to her quickly enough – an amazing thing, if you know children.

‘You are blessed,’ she said, touching our child.

Thaïs nodded.

Banugul turned to me. ‘You wanted a son?’ she asked.

I suppose that I frowned. I wanted Eurydike. I couldn’t remember a time when I had wanted anything else. ‘No,’ I said.

‘You areblessed,’ Banugul said, in her seductress’s voice. It wasn’t human, that voice. It was the sound of man’s desire for woman made flesh. But she was speaking to Thaïs.

And her sister kissed our daughter on the forehead. ‘I never had a child by Memnon,’ she said, with what sounded to me like genuine sadness. ‘You are very brave. Yes?’

Thaïs shrugged.

Women can be such cats to each other. But these two seemed to be above such stuff. Barsines leaned forward. ‘I was afraid to bear him,’ she said. And then looked confused, because she had said too much. ‘I loved him – too much.’ She looked at the rug on the floor of the tent.

‘Memnon?’ Thaïs said. And I realised that she had killed this woman’s husband – that Barsines, for all her seductive ways, had loved Memnon – it was graven on her face – and that Thaïs was just now understanding what every soldier learns – that every corpse you make had a sister and a brother and a wife and some children.

Eurydike had had enough of the strange princesses and came to me, and then raised her head. ‘You smell,’ she said. And giggled, aware that she was the centre of attention, and happy about it.

‘And you will have another child,’ Banugul said. She was openly curious. ‘You, who were reputed to be as beautiful as we?’

Thaïs laughed aloud. Whatever she had been thinking, the sheer hubris of Banugul’s comment didn’t gall her – it amused her. ‘I don’t think I was ever as honey-golden-beautiful as you,’ she said, coining a fine Greek word like any good poet. ‘But I do hate being pregnant. And yet . . .’ She took Eurydike back. The child glowed, put her arms around Thaïs, and said ‘Mummmmmy’, in her too-cute-to-live little-girl voice.

Thaïs rolled her eyes, and all three women laughed.

‘Beauty fades,’ Thaïs said.

Barsines nodded. ‘I try to make myself ready,’ she said. ‘Because I do love it.’

Banugul laughed. It was a laugh of bitterness.

Thaïs clutched her child. ‘I’m sorry,’ she said suddenly to Memnon’s wife.

Barsines had tears in her eyes. ‘Whatever for?’ she asked.

She’s sorry, now that you prove so human, that she killed your man, I thought.

The next day I donned a good chiton and military sandals and went to attend the king. He’d received a formal letter from the Great King of Persia. He presented it to us – a plain letter on good papyrus, not a purple parchment with golden ink, as I’d been led to expect by Herodotus, but such things are often exaggerated.

Darius referred to Alexander, not as a fellow king, but in a slighting manner, and asked for the return of his wife and mother and his eldest son, and he offered to cede to Alexander about a third of the empire. It was a curious letter, full of false pomp and oddly arrogant for a man who ‘begged’ for the return of his wife.

We debated the letter after a fine dinner, the way Athenians debate the role of love after a symposium. As you might expect, it broke down into an argument – a nasty argument – between the two factions. The older men, Philip’s men, were for agreeing to its terms, and the younger men were for rejecting them out of hand. Despite the slowness of the siege, every one of us was sure we’d take the place. It would take time. But we were winning. The Persian Empire was beginning to shred itself – satraps were negotiating through Thaïs’s people, or directly with our king. Athens continued to sit on the fence.

Alexander stayed carefully silent.

When everyone had had too much wine, Parmenio rose to his feet and raised his cup. ‘If I were Alexander, great King of Macedon, I would accept this offer, and be done with war – victorious King of Asia.’ He raised the cup and drank.

Alexander took the cup next and smiled into Parmenio’s eyes. I thought for a moment that he meant the two of them to be reconciled.

He raised the cup. ‘If I were Parmenio,’ he said with careful malice, ‘I would accept.’ He drank the wine, and Parmenio’s face flamed with humiliation.

I helped draft the letter to Darius. A group of us did – Hephaestion, Amyntas, Nearchus, who was down in our camp for a visit.

But Alexander set the tone.

‘Your ancestors invaded Macedonia and the rest of Greece and did us harm although we had not done you any previous injury. I have been appointed commander-in-chief of the Greeks, and it is with the aim of punishing the Persians that I have crossed into Asia, since you are the aggressors. You gave support to the people of Perinthus, who had done my father harm, and Ochus sent a force to Thrace, which was under our rule. My father died at the hand of conspirators instigated by you, as you yourself boasted to everybody in your letters, you killed Arses with the help of Bagoas and gained your throne through unjust means, in defiance of Persian custom and doing wrong to the Persians. You sent unfriendly letters to the Greeks about me, to push them to war against me, and sent money to the Spartans and some other Greeks, which none of the other cities would accept apart from the Spartans. Your envoys corrupted my friends and sought to destroy the peace that I had established among the Greeks.

‘I therefore led an expedition against you, and you started the quarrel. But now I have defeated in battle first your generals and satraps, and now you in person and your army, and by the grace of the gods I control the country. All those who fought on your side and did not die in battle but came over to me, I hold myself responsible for them; they are not on my side under duress but are taking part in the expedition of their own free will. Approach me therefore as the lord of all Asia. If you are afraid of suffering harm at my hands by coming in person, send some of your friends to receive proper assurances. Come to me to ask and receive your mother, your wife, your children and anything else you wish. Whatever you can persuade me to give shall be yours.