The first time I saw Mary Beard, I was 17. It was 1989, and she was speaking at a joint open day for the Oxford and Cambridge classics faculties. She was utterly unlike the other speakers, who, as I recall them, were Oxbridge dons straight from central casting: tweedy, forbidding, male. Instead of standing at a lectern like everyone else, she perched rakishly on the edge of a desk. She was dressed in a vaguely hippyish, embroidered black dress, and a cascade of black hair tumbled around her shoulders. Greg Woolf, now director of the Institute of Classical Studies at the University of London, recalls another one of those open days, in the early 1990s. “I spoke, and then another big hairy bloke like me spoke. And then Mary came on and said: ‘Well, you’ve heard what the boys have got to say.’ And you could see that she’d already won everyone’s hearts.”

Everyone who has met Beard seems to have a story about encountering her for the first time – usually involving her rigorous intellect, her total lack of formality, and her sense of mischief. One of her former students, Emily Kneebone, remembers supervisions – one-to-one or two-to-one teaching sessions – at Newnham, the women-only Cambridge college to which Beard has been attached for most of her adult life, first as a student, then as a don. She would teach from a chaise longue: “At first she’d be in a normal position, but as the hour progressed she would gradually slide further and further down so you could only see her feet.” One junior colleague still remembers Beard introducing herself, at a conference almost 25 years ago, with the overture, “Give us a fag, darlin’.”

In public, in private and in her academic writing she is sceptical, wary of consensus, the kind of person who will turn any question back on itself and examine it from an unexpected angle. She is not afraid to take apart her own work: at that same conference in the early 1990s, she presented a paper that repudiated one of the scholarly articles that had helped make her name a decade earlier, an influential study of Rome’s Vestal Virgins. It was an extremely unusual thing for a scholar to do. “She doesn’t let herself off – she’s not one of those scholars who is building an unassailable monument of work to leave behind her,” Woolf said. “She is quite happy to go back to her earlier self and say, ‘Nah.’”

The learned but approachable figure you see on TV translating Latin inscriptions, carving up a pizza to explain the division of the Roman empire, or arguing about public services on Question Time, is precisely the Beard you encounter in private, except that in real life, she swears magnificently and often. (“She’s always spoken fluent Anglo-Saxon,” said Woolf.) In a Greek restaurant in London one January afternoon, her long grey hair uncharacteristically glossy and fresh from the stylist, Beard talked about everything from Islamic State to academic freedom. At one point, she sketched out an argument for a second referendum on Britain’s membership of the EU. Her case rested on the very nature of democracy, for which the presence of a ballot box was a necessary but not sufficient condition. Democracy cannot properly operate without knowledge, she said – which the entire electorate of summer 2016 lacked. (“Aristophanes knew that!”) The referendum then, should not be treated as the final word, she said, but as a straw vote. “Sure, say we want to leave, but you can only in the end say we are going to leave when we know what it means. Otherwise,” she said, “it’s just wanking in the dark.” Thinking I had misheard, I asked her to repeat. “Wanking in the dark,” repeated Beard, at volume. Later in the conversation, she told me she was planning to get a pink streak in her hair. “I’m fucking well going to have one: it just feels like such fun.”

Beard is a celebrity, a national treasure, and easily the world’s most famous classicist. Her latest book, Women and Power, about the long history of the silencing of female voices, was a Christmas bestseller on both sides of the Atlantic. In the eight years since her debut TV documentary, Pompeii, she has conquered the small screen. She is one of a trio of presenters who will, in March, front Civilisations – a new, big-budget version of Kenneth Clark’s 1969 series Civilisation, the most revered cultural TV series in the BBC’s history. ...