Belle de Jour unmasked: she’s a research scientist

The identity of Belle de Jour, the woman who wrote of her experiences as a London escort in a series of blogs and books which became the TV series Secret Diary of a Call Girl starring Billie Piper, has finally been revealed. She is a 34-year-old scientist called Dr Brooke Magnanti who decided to come clean and tell the Sunday Times columnist India Knight of her secret, in order to foil a Daily Mail scoop.

Magnanti works at the Bristol Initiative for Research of Child Health where she told her colleagues her secret last month. They were, she said, amazingly kind and supportive". They are, incidentally, all women.

Not even Belle's literary agent was aware of her true identity, which has led to considerable speculation about who was writing the blogs and books. The novelists Isabel Wolff and Sarah Champion have both been suspected, as has the former Erotic Review editor Rowan Pelling. Many thought it was a man masquerading as a woman - and Toby Young was a prime suspect.

No one suspected a young woman with a PhD in informatics, epidemiology and forensic science.

Magnanti took her pseudonym from the 1967 Bunuel film Belle de Jour starring Catherine Deneuve as a comfortably-off housewife who turns to prostitution out of boredom. Magnanti's motive, however, was not boredom but financial necessity: in 2003, in the final stages of her PhD, she ran out of money.

Unable to afford her rent, she says she asked herself: "What can I do that I can start doing straightaway, that doesn't require a great deal of training or investment to get started, that's cash in hand and that leaves me spare time to do my work in?" She joined a London escort agency and the rest is history.

Did she have any regrets, India Knight asked her? "I've felt worse about my writing than I ever have about sex for money," she said.

Magnanti spent 14 months as an escort, charging £300 an hour, of which £100 went to the agency and she kept £200. She cannot remember how many men she slept with - but it was "somewhere between dozens and hundreds".

Asked why she had decided to come out, Magnanti told Knight that anonymity had become no fun - "I couldn't even go to my own book launch party" - but there was also an ex-boyfriend with a big mouth "lurking in the background", as Knight put it, and she had decided to get in first.

The Daily Mail, clearly miffed by the Sunday Times expose, claimed today that the boyfriend was an Army officer called Owen who was aware of Brooke's blog but "was so blinded by love that he buried his head in the sand, refusing to read the blog in detail until they broke up a year ago".

What happens to Belle de Jour now? There are still two more books in the pipeline and she's keen to wrap up the blog with a happy ending. "Then I'd like to go back to studying cancer epidemiology and etiology: the causes of cancer and the diagnosis rates. They're my thing."