Billie Piper, <EM>Secret Diary of a Call Girl</EM> Billie Piper, Secret Diary of a Call Girl
Billie Piper is a nice girl who follows her instincts, for better or for worse. That's how the British actress, who'll be familiar only to Doctor Who fans and close followers of the U.K. tabloid press, came to play a high-class hooker in Showtime's controversial new series, Secret Diary of a Call Girl

(Mondays at 10:30 pm/ET).

"It's not a shock-factor thing for me," says Piper. "I just thought about playing the part and what it meant emotionally, as opposed to, 'I'm going to get my t--- out.' You can't tell a story of that nature without showing the truth. I wanted it to be really honest."

It may well be Piper's honesty, cou­pled with the fact that she's grown up in public, that has led her to become a U.K. tabloid target. She's moved out of London to a country cottage in West Sussex because of persistent paparazzi hounding. And yet she welcomes a TV Guide reporter into her new home like an old friend. Then it's off to a local pub, with Piper in track pants and a hoodie, to talk about everything.

Lucy Prebble, Call Girl's creator, says it's this openness that made Piper right for the role of Belle, the show's, er, titular character. "Billie is great firstly because she's a top-rate actress," Prebble says. "Secondly, she is very likable, a rare qual­ity and a good one for a character who does something so morally problematic for a living. She's also wonderfully curi­ous as a performer and a person, which really helps the spirit of the material."

"The material" began on the Web. In 2003, a London woman calling her­self "Belle du Jour" started writing a blog about her adventures as a high-class hooker. Far from just trash-talking, this prostitute was sassy, self-aware, loved her job and made good money. And she was popular — Belle's blog soon morphed into a best-selling book, and then the U.K. TV series. It was a hit, helped in part by a bout of media hand-wringing about whether it glamorized prostitution or empowered women.

To add just a little more spice to the pudding, Piper's early career trajectory in England bears an uncanny resem­blance to that of one B. Spears. A teen­age pop sensation, she became tabloid cannon fodder after a questionable marriage, at 18, to radio and TV host Chris Evans, 34, who proposed on his radio show and left a silver Ferrari filled with roses outside her house. The pair spent the next two years on an extended, notoriously hedonistic vacation. She's now married to actor Laurence Fox (Becoming Jane), who apparently doesn't mind her sexy new role: "He tells me how he would do it! It's not like he shies away from it. He's really helpful."

When Piper announced in 2003 that she was returning to acting, she was widely written off as another pop star–slash–whatever, but she soon turned in a series of performances that silenced the naysayers. A role in a BBC retelling of Chaucer's The Canterbury Tales was followed by Doctor Who, in which she plays the good Doctor's street-smart sidekick, Rose Tyler.

Then there was a series of one-off dramas covering everything from Shake­speare to Jane Austen, proving that she was adaptable as well as talented. Even so, her latest role seems deliberately contrary — this is a show where the sex scenes are pretty much the only scenes.

"Someone said to me the other day, rather viciously, 'What A-list stars do you see get their t--- out?' And then I suddenly start thinking, 'Oh, my God, what have I done? I've ruined my future career!'" Piper says. "If people get upset about the show, that's fine. But you know, you get photographed on the beach topless nowadays. After all, they're only breasts. It's not that interesting."

Fortunately, Secret Diary of a Call Girl is.

Use our Online Video Guide to watch clips of Secret Diary of a Call Girl.

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