Belle de Jour is coming to town on Sunday to shake the Oxford Literary Festival’s traditional foundations to the core. Her latest book about life as a London call girl is titled Belle’s Best Bits. But if these are the best, what are the worst? Katherine MacAlister finds out.

For those of you who have been hibernating under the stairs, Belle de Jour is the new literary phenomenon whose call girl blog turned into an entire Billie Piper mini series and a stack of best-selling books.

The icing on the cake was when Belle’s anonymity was then shredded by an ex-boyfriend and the high class hooker was unearthed as Dr Brooke Magnanti, a research scientist specialising in childhood cancers, who supported herself by working as a call girl while completing her doctoral studies.

Could it get any better?

Yes, actually, because having just interviewed her, Brooke is still a force to be reckoned with, entirely unrepentant and impossible not to admire, whether you agree with her principles or not.

So is she nervous about her Oxford engagement?

“I don’t know. Should I be? Because I can start panicking now, there should be plenty of time to whip myself into a good old-fashioned paranoid froth. Actually, I’ve heard it’s a nice crowd, so probably no need to worry,” she says, warming me up for a bruiser of a chat. As for whether the Oxford Literary Festival is ready for her? “Probably. They have beds there, right?”

And yet Brooke, 35, hadn’t planned to be this famous.

She began her blog when she became a call girl, but had no idea how popular it would become (15,000 hits a day).

“When I started blogging, there was no such thing as blog-to-book,” Brooke remembers. “It was a surprise to learn anyone was reading it, let alone literary agents. The blogging world was still very small and new at the time.”

Nothing gets to Brooke, nothing that she’d let on anyway. And one suspects that’s how she survived surprisingly intact in the world of prostitution, even though there were a few close shaves.

“I was scared once or twice. But I believe in staying sober, aware, and getting straight out the door if you have even the slightest reason to doubt someone. Better safe than sorry. No money is worth that.”

Neither has Brooke’s life as a call girl affected her career or love life.

“I told my boyfriend as soon as I started thinking of him as something more than a casual fling,” Brooke tells me. “He took it well – he’s not naive. I think he struggles when criticism upsets me, but otherwise it’s in the past. He’s a keeper. And sex is still vital. For me, it’s unspoken communication. You need passion as well as friendship and commitment to make a relationship work.”

So while it would appear as if the lives of Belle and Brooke are worlds apart, one having sex in London’s smart hotels, the other locked in a Bristol lab, the woman herself says there’s not much to distinguish between them.

“I’m Belle every day,” Brooke says. “We’re not different people. And I love my job – it’s why I did the sex work, to finish the PhD. The doctorate is your licence to practice science, and I never lost sight of that.

“And we’re not that different. Belle wears a bit more makeup and Brooke does a lot more knitting.

“I still say things like ‘orthogonality’ regardless of the audience, and no amount of designer clobber can hide that fact that I’m a nerd.

“My prospects are more or less the same at this point in my career as they would have been had I not come out. My current employers have taken a very supportive stance and everyone seems to be following their lead. So yes, it was worth it. My visa prevented me from working more than 15 hours a week (Brooke is American and was on a student visa at the time). If you happen to know a Starbucks where I could have made the same rate as I did in sex, let me know.”

OK, but isn’t a bit weird for her fellow workers, knowing that they are working with such notoriety? “Most people in my real life know me as a scientist first, so the Belle de Jour thing is like an extra anecdote, one more reason for them to take the mick in the pub.

“Because of the situation with my ex, the police have co-operated in keeping my address out of the public record. Apart from that I go about as I normally do. I still work in the same office, though we do have more security in the department now. I think it’s harder for actors, most people never get to see them outside of the roles they play.”

By actors, Brooke is talking about Billie Piper who played her in the hugely successful ITV2 series Secret Diary of a Call Girl, the third series having aired in January. “Billie was very nice, very professional. I think she portrays the sex work side of things very well, but I do worry that her character doesn’t seem to have many friends or hobbies,” Brooke adds.

The main criticism of Belle has been that she glamorises the profession, something Brooke immediately refutes as being “ignorant and misinformed. I find it amusing that people with no knowledge of sex work like to tell actual sex workers their experiences are false and invalid.

“It would be funny if it wasn’t so patronising.”

Perhaps what disconcerts them is how easily Brooke slid into her role as Belle. Is this because she had a strong sex drive to start with? “I do have a high sex drive but sex on the job is more about performance, not appetite. It would be a little like asking Heston Blumenthal if he needs to be hungrier than the average bloke in order to cook well.”

So what does ruffle Brooke’s feathers? “Child abuse, voter apathy, and the price of avocados in this country.” she says flippantly.

But that’s Brooke all over, she’s very honest and open, while revealing very little of herself.

And yet, it’s a well documented fact that when Brooke was initially exposed to India Knight in The Times, she had yet to disclose her chosen profession to her mother who lives in the US.

“She’s a cool lady,” Brooke says quickly. “Her copy of Guide to Men was the first one of my books I ever signed.”

Brooke’s estranged father has also appeared in the press, blaming himself for Belle’s chosen profession.

Paul Magnanti recently admitted to using prostitutes after his divorce, some of whom briefly lived with him despite their drug problems, and therefore met his daughter.

But Brooke quickly dismisses his theories: “I moved out of home and went to university at 15, four years before my parents divorced.

“I didn’t live with him at any point after that, and I never had a problem with the prostitutes – it was the drugs that bothered me. I think his Catholic upbringing is getting the better of him.”

So there you have it, all or nothing, depending on which way you look at it. But does Brooke worry that Belle de Jour will come back to haunt her when she least expects it, say when she has children?

“It may come as a complete surprise to learn ALL children are embarrassed by their parents, regardless of what they do. I don’t expect mine to be any different.”

Good luck to her interviewer India Knight then, so what does Brooke think they’ll talk about on Sunday? “I imagine she’ll want to follow up on what the fallout has been like after her interview. She warned me at the time – wondered if I was prepared for what was to come. I imagine she’d be curious about that.

“Because it just caught people on the back foot, didn’t it? Someone who works in childhood cancer research.”

One thing’s for sure, if this interview’s anything to go by, Brooke’s appearance at the Oxford Literary Festival should be riveting.

Belle de Jour is in conversation with India Knight at the Christ Church Marquee at 2.00pm on Sunday. Go to oxfordliteraryfestival.com for more information.