From her award-winning turn as a shy self-harmer turned provocateur in Secretary to her recent role as a recovering junkie in SherryBaby, Maggie Gyllenhaal has long been the poster girl for disenchanted heroines, wowing the critics and attracting a legion of fans.

As she sits coyly twisting her hair in a plush penthouse, just blocks away from where she resides in downtown New York with her actor partner and new baby Ramona, the pretty actress freely admits that her extra-curricular credentials are in pretty good shape too.

But even as model for some of the world's top fashion houses, sister to one of Hollywood's hottest actors and with a slew of awards to her name, it is her role as Rachel Dawe's in Batman: The Dark Knight that has whetted the appetite of fans and critics alike, paving the way for maintream superstardom.

If Gyllenhaal has any qualms about the transition, she shows little sign of it. Nor does she show any concern about picking up the reigns from one half of star-studded couple Tom-Kat. "I'm not walking into Katie’s [Holmes] performance,” she explains. “I'm thinking of it as an opportunity to play somebody who's alive and smart. Chris [Nolan, the director] asked me to do this because he wanted me, not because he wants some generic lady in a dress.”

Continues the actress: "The part came up and something about it just appealled to me. It was just well written and fun. And the opportunity to work with director Christopher Nolan and an actor like Christian Bale was just to good to pass up."

Obsessively guarded about her private life and fiercely protective about her film choices, Gyllenhaal's spot as the romantic lead in the multi-million dollar Batman franchise, heralds a significant career move for her. Indeed, insiders have said that she almost turned down the role because of it’s blockbuster appeal. Gyllenhaal admits it has been a rite of passage.

"Doing Batman has shocked me at every turn. When I started, I thought, 'Well, it's a huge movie, I'll just do my best to put what I can into it.’ But, in fact, they've been really hungry for my ideas, for my views. It's great. They've been asking for more.

"I'm really excited about it. I mean, it's not some silly action movie: Chris Nolan is directing, Christian Bale's starring."

Currently filming in Chicago, the cast of Dark Knight is already being hounded by the press both on set and off for inside information about the plot and the chemistry between Gyllenhaal and Bale. It's an aspect of the job that Gyllenhaal would rather forget.

A recent shot of the actress caught unaware, breast-feeding in public ended up splashed onto the internet, sparking hours of debate and thousands of web hits. Such constant scrutiny takes its toll. "Some days it feels like they [the paparazzi] are everywhere: it's intrusive and unnecessary. I go out for a carton of milk and they are there.

"It's like there's this constant fascination with celebrity right now, which seems extraordinary to me. We don't want it and we just try our best to avoid it as much as possible. But it doesn't stop it being very upsetting."

The actress admits that starting her own family, with fellow actor Peter Sarsgaard has changed her perspective slightly about the roles she picks.

"Initially I thought that if it doesn't seem like I can do a good job and have a good time, I don't want to do it. I don't want to just do some little movie because it looks interesting, I have to think strategically. It's to do with Peter and making sure our family comes first."

Strong family values have been engrained in Gyllenhaal from a young age. Brought up in the business courtesy of her director father, Stephen, and mother, screenwriter Naomi Foner, Gyllenhaal's brother Jake has also enjoyed box office success. While reputedly very close, the actress is keen for them to be judged on their own terms, visibly irked by the common assumption that they work together regularly. A fallacy, says Gyllenhaal, and not something that she has any plans to repeat. "People ask a lot about this and you know I won't work with him again on-screen, not for a long while anyway. It's important to do our own thing. I want to get away from that now."

A close knit family, Gyllenhaal's first film role, Waterland, was directed by her father. But it was cult sadomasochistic romance, Secretary in 2002 that really propelled Gyllenhaal into the limelight as well as a series of high profile supporting roles, in the Spike Jonze film Adaptation and Mona Lisa Smile, starring Julia Roberts.

A politically active Democrat, the actress very publicly drew fire at the Tribeca Film Festival in 2005 after she reportedly suggested that the United States should accept "some responsibility" for the September 11 attacks. A lesser actress may have been shunned; not Gyllenhaal. She would later be offered a part in Oliver Stone's 2006 film, World Trade Center.

While Gyllenhaal quietly craves an inconspicuous life away from the lens, the actress is smart enough to know that the industry has no room for such luxuries.

"I can’t complain,” she concedes. “Whether it's Batman or Secretary, I have the opportunity to make movies that affect people.

"And if something touches my soul or anyone elses, it's worth doing."

The Dark Knight is due out in Spring 2008.