FOR an actress who had only previously played characters such as "young girl in a bus station" in low-budget Scottish films, it was a role which brought about a transformation. Having moved up from small walk-on stints, and regular parts in a comedy sketch show, to a key part in one of Britain's most cherished and long-running television series, Doctor Who, Karen Gillan says she was overwhelmed by her overnight fame.
It's perhaps little wonder, given she had not enjoyed the stage school childhood common among today's leading television stars to prepare her.
She cut her teeth in youth theatre, playing Liesl in a school production of The Sound of Music in Inverness, where she was raised by her father, John, who works in a daycare centre, and her mother, Marie, who works in a shop.
Now, having followed in the footsteps of women including Bonnie Langford, Billie Piper, Catherine Tate and the late Elisabeth Sladen, to play the role of the Doctor's companion, Gillan says she is relishing her career. Since making her debut in the programme a year ago this month in a kissogram police uniform, she and Matt Smith, the Eleventh Doctor, have won a legion of fans and given renewed impetus to a show which regularly attracts at least six millions viewers.
Remarkably, she was not even familiar with the show when she auditioned for the part of Amy Pond. Speaking on the Doctor Who set, it is evident that Gillan is now fully up to speed with the show's history and heritage, dropping dark hints about momentous events ahead in the new series, which begins tonight on BBC1.
As we speak, Lily Cole, a six-foot actress and model, wanders past. She is painted green and wearing a pair of slippers. Such sights would be strange indeed anywhere else, but on Doctor Who such sights occur about twice a minute. It is, Gillan says, a part of the job she loves: "It just gets better and better all the time because you've got more invested in it. It's always developing and evolving. So it doesn't get boring because you're doing a different thing every week."
Gillan, 23, who went to Charleston Academy in Inverness, it seems, is slowly coming to terms with having her world turned upside down. Only last summer, she launched an action figure of her character in person at a Glasgow shopping centre – as sure a sign as any of having "made it".
Thankfully, she says, her fame has not reached a level which makes her feel uncomfortable in her personal life. She has been with her boyfriend, photographer Patrick Green, for five years, but chooses not to feature in newspaper gossip columns.
Whereas Matt Smith claims he now has to wear hooded tops to avoid being recognised while out shopping, Gillan hasn't been bothered too often by fans. "It's been fine," she smiles. "Nothing terrible's happened yet – touch wood. It was kind of overwhelming at the beginning because it's just so instant, but then you get used to it."
Having impressed the team behind the Doctor Who series – including Steven Moffat, the show's lead writer and executive producer – with her portrayal of Amy, Gillan is now fully part of the programme's family.
It is, the 5ft 10in former model admits, a close-knit clan which works hard – making just one series means working nine months, 12 hours a day, with only one day off every 11 days.
Ahead of the new series, fan websites are teeming with speculation about what adventures await, poring over the official trailers frame by frame for clues. But the camaraderie of cast and crew means that plots are guarded with the utmost secrecy.
When we meet, the team are filming what will be the third episode of the new series, the pirate-themed The Curse Of The Black Spot. Other cast members, including Smith, have walked past with black spots painted on the palms of their hands, but none of them are willing to explain their significance.
Gillan, too, assumes a veteran's air when discussing potential storylines. When she was told she had won the part of Amy, she had to keep it quiet, and only told her parents an hour before it was made public. Such discretion has remained with her.
"There are going to be a lot of revelations," she suggests tantalisingly. "There's one huge one that will change everything. Steven Moffat went around everybody and only told them the bits they needed to know, and we're not allowed to discuss it with each other, which is really relevant for the whole story."
One rumour has it that her character's husband, Rory, now wears the trousers in their relationship since the pair got hitched. Gillan is having none of it. "Absolutely not!" she shouts, with the kind of look on her face that would stop a Dalek in its tracks. "That's not true, no. The thing is, Amy just lets him think he is!"
Gillan, a willowy redhead who left school at 16 to study drama at Edinburgh's Telford College, is having the time of her life, whatever the new series holds, and she is picking up some interesting new skills along the way. An excitable presence, she is quick with her answers and has a good sense of humour. She says that the episode they are filming has been her favourite so far because of her pirate-style costume and the fact she gets to do some sword fighting.
"Everyone was really nervous when I got a sword in my hand, and quite rightly so," she grins. "But actually, I was rather co-ordinated, which surprises you all, I bet. I really, really got into it, and I would like to take up sword-fighting as a hobby."
Given the calibre of actresses to have become companions to the Time Lord before her, it might not seem unreasonable to assume Gillan – who previously enjoyed parts in Channel 4 sketch series The Kevin Bishop Show and Rebus – felt overawed at filling their shoes. Yet she has made the role her own, playing Amy with a Scottish accent, and gradually allowing the character to develop. It is clear she is fond of the character and keen to show she is more than just an action hero. "With the last series, I wanted to keep her guarded. She doesn't like to show her emotions because she wants to be strong," Ms Gillan reveals. "But in this series, there are cracks starting to form in that exterior and we're starting to see other aspects of her.
"Actually, in one episode we've just filmed, it was really difficult because it was about something I've never experienced before," she adds, cryptically. "I didn't feel as if I could relate to it because it's never happened to me.
"I had to go and talk to quite a few people so I could gauge how that would feel. It was a massive thing that happens, and I can't tell you what that was!"
Such challenges and rewards are not going to end any time soon. As an established part of the show, Gillan even has her own ideas of where The Doctor and his companions might end up in future episodes. "I always think I'd like to go back to the 1960s," she muses, before conceding: "But that wouldn't be very exciting for Doctor Who, because what would the monster be?"
However, she will be travelling back to that decade while playing legendary model Jean Shrimpton in forthcoming BBC Four drama We'll Take Manhattan, which focuses on The Shrimp's relationship with photographer David Bailey.
"I can't wait," admits Gillan. "I'm already well into my research now and I just love that period. When that script came along I was like, 'This is perfect for the first thing that I do after I finish Doctor Who.'
"So this'll be my first venture outside of Doctor Who, scaring me slightly but I'm just so looking forward to it. I just find it such an interesting, fascinating period."
It is back to the Tardis for the time being, and as if seeing the sets and meeting the cast isn't exciting enough, she has a few final words to whip aficionados of the series into even more of a frenzy. "The thing about this series is it's much more ambitious than the previous one, just in terms of the scale of it," she said.
"We're opening with a two-parter, which we've never done before, and we're off to the States, and then we're straight into a pirate story, which is a huge production.
"All the elements came together. Oh yeah, and the monsters are the scariest ever!"
• The new series of Doctor Who started last night on BBC1 at 6pm.
TOUGH ACTS TO FOLLOW
BILLIE PIPER (Rose Tyler)
Joined Christopher Ecclestone, the Ninth Doctor, for the revival of the show in 2005, and stayed with him as he regenerated into David Tennant. Playing a strong, vibrant character who was easy to relate to, Piper helped build a new audience for the show.
LOUISE JAMESON (Leela)
Remembered as "The one with the leather", Leela was a noble savage who travelled with the Fourth Doctor, Tom Baker, before marrying a Gallifreyan. Jameson has since become a soap stalwart.
LALLA WARD (Romana)
A fellow Time Lord, Romana was foisted on the Fourth Doctor to help hunt for the Key to Time. Mary Tamm played her originally but Ward was better remembered for her chemistry with Baker: they married in 1980 (divorcing soon after). Ward now illustrates books by her husband, Richard Dawkins.
KATY MANNING (Jo Grant)
Starting as a ditzy hippy of the 1960s, Jo became a trusted, resourceful friend to the Third Doctor, Jon Pertwee. Manning's play Me and Jezebel ran at the 2009 Edinburgh Fringe. She has posed nude with Daleks.
ELISABETH SLADEN (Sarah Jane Smith)
The best-loved of all the companions and Who actors, Sarah Jane worked with five Doctors and had two of her own spin-off shows. Lis Sladen passed away on Tuesday. A special tribute will run on CBBC at 6:45pm tonight.