Dakota Blue Richards is saving the world again. It seems to be her thing, these days. For in the family fantasy The Secret of Moonacre, the 14-year-old Brighton-based starlet plays Maria, an orphaned princess who discovers hitherto unexplored magical powers, befriends a fearsome black lion, rides a unicorn, and must ultimately defend the entire planet from a cataclysmic collision with the moon.

Following hot on the heels of The Golden Compass, where, again, Richards took starring duties (opposite Nicole Kidman and Daniel Craig) as the preternaturally gifted heroine Lyra Belacqua (she befriends a giant polar bear, rides him into battle, and basically saves the world), you could be forgiven for thinking that she is the victim of a God complex.

“But fantasy movies are so much fun, and so magical, they’re hard to resist!” says Richards today, sitting demurely in the armchair of a downtown Toronto hotel, where she is promoting Moonacre. She is wearing a little black off-the-shoulder number, and her silky auburn tresses are falling down delicately, framing her alabaster face. She is 14 going on 40, and will later admit: “You’re kind of forced to grow up on these sets, because there’s just so many adults around you. Obviously you don’t want to miss your childhood, but at the same time everyone has to grow up, so why not do it this way?”

For now, however, she giggles with girlish enthusiasm as she describes how she bagged her Moonacre role before she had even finished The Golden Compass. “In one single day I heard about the audition, read the script, learnt my lines for the audition, went to the audition, and got the part,” she says, allowing herself a tiny smirk of pride. Life’s been like that, you see, ever since the Compass hoopla rolled into town.

Before it Richards was just a normal Brighton schoolgirl, and the only daughter of a single mum social worker. Her most significant role to date had been as a sheep in the school nativity play (“But deep down inside I always thought, ‘I’m more than a sheep’ ”). Then, famously, and in a vaguely mythic echo of the film’s storyline, she became the “chosen one” – selected out of 10,000 girls to play the role of a lifetime (and with a stamp of approval from Compass author Philip Pullman, who vetted the casting director’s top 40 choices).

She says that much of what’s happened to her since then, including acting lessons from Nicole Kidman and a worldwide Golden Compass promotional tour, has had a dreamlike quality. “I have moments where I go: ‘How did I get to this point? How did I end up here? And am I going to wake up?’ ” Of course, it hasn’t all been edifying. An hysterical tabloid story that described her vandalising a local Brighton snow sculpture (actually, a snowman, flattened in a harmless snowball fight) gave her a taste of the dark side.

Her mother and grandmother act as chaperones when she’s on set, and keep her grounded when she’s off it too. She has no boyfriend (“It would be a bit odd, because I’m away so much of the time”), and says that sometimes making friends with teenagers her own age can be difficult. “I don’t introduce myself by saying, ‘Hi, I’m Dakota Blue Richards from The Golden Compass’, like Troy McClure in The Simpsons. But they always find out.”

She says that despite the cliff-hanger close to The Golden Compass (Lyra flying off in a Zeppelin, in hot pursuit of Daniel Craig) parts two and three of her big-budget adventures are still on hold. The movie made over $360 million worldwide, but at a budget of $180 million this wasn’t seen as quite the right level of returns. “If they are going to make the other two films, I don’t think they’ll be doing them for some time. They might have to change the cast by then.”

This, ultimately, is good news for Richards, who’s finally getting a chance to flex her non-fantasy-based performance repertoire in the upcoming hard-hitting drama Dustbin Baby (“It’s about the traumas of growing up inside the care system”) and the psychological thriller Lovely to the Last.

She says that, typically, at the end of an interview she says she doesn’t really care about acting in the long term, and that she’d rather do something real, like be a vet or a teacher. But she can’t keep faking it. “I used to say that I didn’t want to get to a place where I was ‘just an actress’,” she says, before giving a little shrug, giving up, and giving in. “But now, I don’t think I want to be anything else.”