Karen Gillan’s life is taking some getting used to. The new Doctor Who girl has gone from anonymity to infamy overnight, with everyone and his wife dissecting the length of her skirts like they were as important as, you know, the General Election and world peace and stuff.

‘People kept saying it was going to happen. But how can you prepare for being famous? Other than be aware it’s going to happen,’ she says. The 22-year-old from Inverness has even experienced her first ‘papping’ – while she and boyfriend Patrick Green, a 24-year-old photographer, were at the garden centre buying bonsai trees, of all things. ‘That was very strange. We just looked like the most boring couple in the entire world,’ she laughs. ‘Not rock and roll at all.’

The actress’s turn as new assistant Amy Pond is going down a storm with viewers, lots of whom are Slightly Fanatical about the cult show. They’re also not backwards in coming forwards when it comes to criticising anything they don’t like, so Karen was ‘a bit scared’ about their reaction to her. Thankfully, fan mail from the Whovian hardcore is flooding in. ‘I’ve had loads of stuff, but nothing crazy yet. Maybe it’ll happen, but the oddest thing so far is people sending me pictures of myself. Opening up an envelope and it’s yourself, it’s like, “Thanks for that”.’

There’s been much raving about the on-screen chemistry between Karen and new Doctor Matt Smith – who looks like usurping David Tennant as the most popular Timelord ever. ‘We worked well together from the start. We’ve got on-screen chemistry – we hope – and we’re working on it every day, trying to make it better.’

Karen loves playing Amy, who she reckons is a tad strange. ‘I think she’s a little bit weird, and I hate to say it, but maybe I fit in to that as well. Matt called me mad as a box of cats. There is no evidence to support that whatsoever,’ she laughs. In fact, Karen claims Matt is the mad one. ‘It’s funny he says that about me when actually he is the mad one. But he doesn’t really know it. Are you mad if you know? You certainly know when he comes in to a room… Matt is very eccentric and has a lot of energy about him.’

Karen says she wants to stick around as part of one of British telly’s biggest institutions for as long as possible. And who knows where it could lead. ‘I don’t know. Perhaps theatre, that’s what I’d quite like to do. I’m not sure about Hollywood,’ she says. ‘But it’s too weird to think anywhere beyond this very moment.’

GETTING AMY POND'S LOOK JUST RIGHT

There’s been a hoo-ha over the sauciness of some of Karen’s costumes. And the actress, who has also done catwalk modelling during dry spells in her acting, was fully involved in creating her character’s wardrobe. ‘It was quite a long process. She’s quite an outcast and I wanted a vintage-y feel, because I thought it’d be nice to have something individual that doesn’t conform to what girls usually wear at that age,’ says Karen. ‘But I think it works going down a slightly more ordinary route as well because she is just an ordinary girl. So she wears high street clothes mixed with one-off vintage pieces.’

Doctor Who is on Saturdays, BBC1