Boris Johnson believes himself to be a reincarnation of Winston Churchill. In fact he much more closely resembles a political figure of an earlier era, the charismatic Athenian chancer Alcibiades. Ward of Pericles, friend and would-be lover of Socrates, serial betrayer, this was the man who did more than any other single person to destroy Athenian democracy by promoting the ultimately catastrophic Sicilian Expedition of 415 BC, yet who remains a figure of seemingly inexpungible glamour.

Well-born (though on his father’s side not quite from the top drawer), beautiful and rich, Alcibiades charmed everybody, except an ever-growing number of enemies, his wife (who left him to live with her brother) and uncounted other spurned inamoratas. His charm was first and foremost physical. “His beauty bloomed with him,” as Plutarch put it, “in all the ages of his life.” Perhaps it was just as well he died before he reached 50.

The second element of his charm was his eloquence. Even in that outstanding age of oratory, Alcibiades stood out as “a master in the art of speaking”. Apparently he lisped (the equivalent of the Boris bumble?) but “his lisping… became him well”. Alcibiades wanted to be more than simply eloquent; he wished to argue as well as Socrates.

The relationship between the ugly, principled philosopher and the beautiful, amoral adventurer is one of the most fascinating in ancient history. Each had something the other desired: Socrates wished to perfect the flawed moral character of his wayward friend, while Alcibiades, by “having” Socrates, wanted to acquire his philosophical depth. Both were destined to be disappointed.

The guiding force in Alcibiades’s character was raging ambition and “the desire of superiority”, combined with an addiction to pleasure. He quickly became one of the best-known, most talked-about men in Athens. Many were seduced, others were more sceptical. Plutarch reports the misanthrope Timon saying: “Go on boldly, my son, and increase in credit with the people, for thou wilt one day bring them calamities enough.” As the great historian Thucydides put it, “the general public became wary of the excesses of his unconventional and hedonistic lifestyle and of the huge ambition apparent at every turn… of his involvement”.

This ambition first came to the fore when Alcibiades entered seven teams for the Olympic chariot races in 416 BC and won first, second and fourth prizes. (He didn’t ride himself, mind you.) This success set him up for other political endeavours, above all his promotion of the greatest military disaster in Athenian history, the armada sent to conquer Sicily in 415 BC.

Addressing the Athenian assembly, four days after the expedition had been approved, Alcibiades held out Sicily as an easy, glorious chance to extend Athens’s imperial sway, with no risks or downsides attached, especially concerning the fleet. (Any parallels with Brexit are utterly far-fetched.) Speaking against him was the cautious Nicias, who asked sensible questions about the advisability of the enterprise and questioned Alcibiades’s motives: “He is only concerned with his own interest… Do not allow this man his personal preening at the city’s expense.”

Nicias even suggested a second vote: “You have it in your power to restore the city to health when it has taken a wrong decision.” He was ignored. The expedition went ahead, with Alcibiades and Nicias as co-commanders, and two years later was almost entirely obliterated, fleet included.

By this time Alcibiades had done a runner. Summoned back to Athens to face trial for defacing statues of Hermes and parodying the rites of the Eleusinian Mysteries, he’d managed to escape. During an extraordinary roller-coaster period, Alcibiades changed sides several times, supporting Athens’s main enemy Sparta, before falling out with the Spartan king Agis, reportedly after Alcibiades seduced his wife. He later switched over to Athens’s other great enemy, Persia (he became a close friend and adviser of the Persian satrap Tissaphernes), then somehow managed to reingratiate himself with the Athenians.

One question Alcibiades’s career raises is whether he ever took anything that seriously (apart from his own fame and glory). He liked to make fun of things, the riskier and less PC the better.

A related question is whether Alcibiades believed in democracy. The answer would probably be: when it suited him. He was happy to play the democratic game early in his career, wooing the people with flattery and theatrics, but showed no compunction in supporting the undemocratic Spartans and Persians. After the oligarchic coup in Athens, Alcibiades, eyeing a return, negotiated with both the democrats and oligarchs.

Rather surprisingly, the Athenian democrats, exiled with the fleet on Samos, voted to bring Alcibiades back and he was given the role of junior co-commander. After a string of naval victories (mainly achieved by his colleague Thrasybulus), Alcibiades enjoyed a triumphant return to Athens in 407 BC, appointed supreme commander by the new democratic regime.

He almost immediately messed things up and was held responsible for a crushing naval defeat. This time there was no way back.

In the Nicomachean Ethics, Aristotle asserts that what he calls “eudaimonia” (flourishing) can only be assessed over an entire lifetime. In this context the closing act of Alcibiades’s life deserves special attention. According to Plutarch, Alcibiades met his end holed up in Phrygia with his latest girlfriend, Timandra, when assassins came and set fire to their house. Alcibiades managed to escape through the flames but was killed in a flurry of arrows.