SOMEWHERE,most likely in a vault, there isawrittenjob descriptionforthe roleof spokesperson forthepresidentof theUnitedStatesof America. Aside from former White House press secretaries such as Marlin FitzwaterandDeeDeeMyers, however, few people can have much ideawhatthejobreallyinvolves. Allison Janney was no exception, but that didn't deter her from taking the part of Claudia Jean "CJ" Cregg, press secretarytoPresidentJosiah BartlettonTheWestWing.

When the first series of the White House drama screened in 1999, Janney became an overnight heroine to millions of women. But she claims to bear no personal resemblance to her character. "Everything CJ was, I'm not," says the 47-year-old. "She oozes power and confidence. That's not me."

Perhapsmostsurprising-fora woman who once said she was inspired by Susan B Anthony, one of the first American suffragettes - is that even after seven years of working in a fictional White House, Janney claims not to be interested in politics. Growing up in Dayton, Ohio, her childhood was politics-free. She was just four when JFK was shot, and doesn't remember being aware of it. "I didn't even know if my parents were Democrat or Republican."

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When we talk, on a day when President Bush is visiting Ohio to plead for "patience and understanding from the American people", she declines to discuss policy - other than to say she'd like to see a woman president. But how does she think CJ would deal with an ongoing situation like Iraq? "With a huge bottle of Exedrine and a great deal of diplomacy," she replies.

Afterwinningthepart,Janneygota unique insight into what it would involve from West Wing series consultant Dee Dee Myers. "The most important thing she told me was that a lot of what goes on in the White House is personality-driven, so as a woman it was twice as hard for her to be in with the right group and know what she needed to know."

In a world in which media managers are routinely derided for manipulating the flow of information, obfuscating agendas and spinning bad news, CJ was an unlikely hero. As the rigorous demands of her job clashed with her personal beliefs, she became the liberal conscience of the West Wing. She was overworked and under-appreciated, and her personal life always took second place. Audiences rooted for her, especially when her Secret Service boyfriend was killedandherfathersuccumbedto Alzheimer's disease. Judging by comments on her many internet fansites, CJ is single-handedly responsible for boosting the number of applications to university political science courses by young women across the English-speaking world.

Janney professes bewilderment that the role became an icon for so many women. "I loved CJ, though. I was her biggest fan. She was funny and sweet and vulnerable."

Thoughadoredbycritics,theshow seemed to lose its footing after the sudden death of cast member John Spencer in 2005. "It all changed," Janney says. "It didn't feel right to go on without him and by then the network wasn't really behind the show any more. You know, reality programmes started to take over and it wasn't the same. I really miss being part of something like that. We were a good team."

Now, just over a year after the series ended, Janney has swapped the verbal jousting sessions and punishing filming schedules for a return to her roots as a jobbing actress. First up is a cameo in Hairspray, a remake of John Waters's belovedly trashy1988coming-of-agemoviethat launched the career of Ricki Lake. This time around another newcomer, Nikki Blonsky, plays the 1960s high school kid who dreams of dancing on the local TV station and ending racial segregation. The remake - which, like The Producers, comes after a hugely successful Broadway musical version of the original - is notable in that it stars John Travolta dragging it up as Mrs Blonsky. Janney, who has a brief cameo as an uptight mother, claims to have "had a ball" making the film.

"I saw the original and I am a huge John Waters fan," she says. "The writers of the new versions are friends, they asked me and I said why not? I'd never done a musical before and I was looking forward to that side of things. I'm not a great singer but I like to dance - yet I'm the only person in the film who doesn't get to do either.'"

Shaking off the expectations and preconceptions that come from playing the same character for seven years might be difficult, but Janney has played several roles involving personalities differing wildly from CJ's harried efficiency. "I love to play disturbed characters. They don't have to be mothers but they do tend to have a screw loose. I like to go where it is dark and deep."

Her supporting roles as Chris Cooper's traumatised drudge of a wife in American Beauty and as Meryl Streep's lover in The Hours proved that she can cope with almost anything that's thrown at her. "When West Wing came along I had just done American Beauty. I wanted the part so badly I had to beg my agent not to let them see that tape because it was light years away from the part of CJ."

Janney's upbringing in Dayton - where West Wing co-stars Martin Sheen and Rob Lowe also grew up - was cosy and relatively carefree. She went to boarding school and spent summers at a farm owned by her grandfather. Her mother, Macy, gave up her own career as a budding actress to marry a businessman. The couple had two boys, Hal and Jay, before Janney was born, and they have remained close as adults, although the hectic filming schedule of The West Wing kept her away from home.

"I missed a lot of family stuff," she says. "When Kenyon College gave me an honorary doctorate I couldn't even make it back for that. I missed the plane and my dad had to go and pick it up for me."

She credits her Kenyon drama teacher Tom Turgeon for instilling in her the discipline she lacked. "He was the one who pushed me. I do have a healthy amount of fear about things. Should I do this role or that one? I still need a push sometimes."

By her own admission, Janney came to acting quite late. Growing up, she was a promising ice skater with dreams of going to the Olympics. Looking at her tall frame, one can imagine her gliding on the ice. But at a teenage party, Janney tripped through a plate-glass door after someone stepped on the hem of her dress. The resultant leg injury - in which she lost "a lot of blood" - meant no more skating, and her prolonged convalescence delayed her enrolment in college for a year.

When she finally went, it was to study psychology. Janney only switched to drama at the end of first term, just as Kenyon alumnus Paul Newman returned to his college to direct a play. She became friends with Newman and his wife Joanne Woodward. "They have always been a tremendous source of encouragement, pushing me to do things."

But even with the support of one of Hollywood's biggest names, she knew she'd always have a hard time getting work. "A casting agent once told me that all I was good for was playing aliens and lesbians. When I said Sigourney Weaver was tall, she said, Yes, well, she is drop-dead gorgeous'. I could feel the tears brimming in my eyes."

Like Weaver, Janney is statuesque. "I'm six-foot tall and it is hard to find a man to stand up to me. Right now we're trying to find someone to play Walter to my Hildy in a stage version of His Girl Friday. We've seen dozens of men and if we don't find the right one soon we can't do it."

Finding the right leading man in her personal life is proving difficult too. She confirms that she has broken up with her fiancé of three years, actor Richard Jenik, a fellow actor who cameo'd in the West Wing but was more recently a policeman in Desperate Housewives. Understandably, she is reluctant to go into details. "It's complicated" is all she will say, but she admits she is pining for Chauncey, their dog, who currently lives with Jenik.

She loves the UK. When she was 25 and working with the Neighbourhood Playhouse in New York, she took six months off to come to London on a scholarship to the Royal Academy of Dramatic Art. "It was a wonderful time, going to classes every day and then to the theatre almost every night with my student ID card - and then back to my tiny room, so small, the door hit the bed when I opened it."

She would like to return. "To do something for the London stage, that would be perfect. Please put the word out." She'd happily come to the Edinburgh Festival too. Stephen"BillyElliot"DaldryandSam Mendes, both directors she has worked with in the past, have sounded her out about possible projects which so far haven't managed to get off the ground. But film has kept her busy. She has small parts in two movies due out later this year: Juno, a comedy, and Margaret, starring Anna Paquin and Matt Damon. Janney is clearly most excited by the latter, a New York-set drama about an idealistic young womanwhoturnsuponherfriends.It'swritten byKennethLonergan,whowrotetheOscar-nominatedYouCan Count On Me. "It's an incredible film. It took me to places I've never been before, I think it is going to make people sit up. I think it is the best thing I've ever done."

But she still displays the typical actor's insecurity about what the future holds and says she is concerned about the young girls who write to her for advice. "I don't want them to think it is all glamorous. I tell them there are long periods when it isn't fulfilling. Kids getting successful at an early age, it's worrying. Let's just say I appreciate things a lot more now."

Janney puts her money where her mouth is, lending her support and time to Modest Needs, a charity that supports the working poor. "I think they often get ignored and it is important that ordinary people don't get forgotten, those trying to do their best but who have to decide between getting glasses for their child or putting food on the table."

Maybe she is not so different from CJ after all.

Hairspray is released on Friday