That sequence of events seemed likely to me as a way of explaining Xanthippus’ behaviour. Many Greek states supported Persia. The Thebans were infamous for being present on the wrong side, mocked and scorned for centuries in Athenian drama. Queen Artemisia of Halicarnassus also worked with the Persians. She was presented by Herodotus as a sympathetic character, perhaps in part because he came from the same place. It might look like treason today, but the idea of the nation state had not yet taken root.

Miltiades died a prisoner, in 489 BC, the year after Marathon. Xanthippus was ostracised, or exiled, five years later, in 484 BC, after a public vote. Pieces of pottery, ‘ostraca’, from that event with his name inscribed survive – one with two lines of verse scratched into the surface. It mentions an injustice in politics as the reason. We cannot know for certain whether it was the trial of Miltiades, though that seems likely. Nor can we know the exact part Themistocles played, though it is true that both Xanthippus and Aristides were ostracised by public vote. With the death of Miltiades, that left Themistocles effectively as first man in Athens. Despite the slow reveal, it does look like a campaign by a man famous for his persuasiveness. Only an extraordinary event would force Themistocles to use his influence once again – to reverse the ostracisms and bring good military men home. That event was the invasion of Greece by Persia.

It is true that Themistocles persuaded the Assembly of Athens to use the windfall of silver from a new seam at Laurium to build a fleet of one hundred and eighty ships – a fleet that would be instrumental in evacuating Athens. Themistocles literally saved his city – with three brilliant ideas. This is the story of the first of the three. The Greeks did not take the favour of the gods for granted, but there are times when it looked as if they were rather blessed …

I have compressed the timeline between Marathon and the Xerxes invasion – there was only one ostracism vote allowed per year, for example, which is sensible, but it robs a narrative of a little dramatic energy. I’ve kept the main events as they happened, however. I think it is a fascinating tale and Themistocles was a brilliant man, often overlooked as a key historical figure. The scene where Aristides wrote his own name on a shard of pottery for an illiterate man to vote is well attested – and a fascinating clue to the nature of Aristides.

In Persia, the death of Darius interrupted the terrible vengeance he desired. It is true that he shot an arrow as his vow and had a slave whisper three times each evening for him to ‘Remember the Greeks’. Yet it would be his son Xerxes who brought the army and the fleet to Greece, crossing the Hellespont on two bridges of ships to do it. The detail of his wife giving thanks to the god Ahura Mazda by burying children alive is from Herodotus.