After a couple of glasses of Côtes du Rhône, London's prettiest potty-mouth is "desperate for a piss". This does not bode well. From experience, actresses' convenience breaks, punctuated as they are by tortuous re-beautification, tend to be marathon affairs. It is not uncommon for a radiant diva to emerge only to find their formerly clean-shaven interviewer has grown a beard and the governments of three countries have changed.
But here's a rare thing. Before you can say "Jimmy Riddle", Sophia Myles is sashaying back to the sofa. The whole episode has lasted less than two minutes.
"I know, I am incredibly fast," deadpans Myles, her low vowels loitering somewhere between the Home Counties and the Estuary. "I always beat men for speed. I think it might be my party trick. And I don't wing it - I wash my hands properly and everything. I'm the fastest wee-er anywhere. I should put that on my CV."
That CV is already looking cluttered. Myles, 26, has, by her own admission, been "Britain's next big thing for the past 10 years". She has, for instance, starred in big-budget Hollywood movies: as Lady Penelope in Thunderbirds, and Isolde in Tristan + Isolde. She has brought a soul to lust-object figures in low-budget numbers such as Art School Confidential and the soon-to-be-released Hallam Foe. She has paid the bills in Heartbeat.
We meet in the bar of a central London hotel, where media people come to sit next to other media people and bellow into their mobile phones. The location was Myles's decision, and it seems like an odd one. We know each other, a little, from way back. She was, briefly, the girlfriend of a school friend of mine (who, with a prescient nod to her burgeoning film career, was called Tristan), and we have stayed in touch ever since.
So why we are meeting here, rather than in her flat in Queen's Park, north-west London, is tough to fathom. Her forthcoming appearance in the BBC's Christmas special - a one-off, big budget adaptation of Bram Stoker's Dracula - may hold some clues.
"After I finished filming Dracula," says Myles, "I thought I'd quite like to paint one of the rooms in my flat this really cool blood-red that I'd seen on set. I got myself down to Homebase, picked the paints, and did it myself. But when I woke up the next morning, it looked as if a mental outpatient had started a bloodbath in my flat. I had to get the professionals in. I now realise I'm not a natural domestic goddess."
This is typical Myles, playing the happy, daffy ladette; the fastest wee-er in the West. Although she is currently cock-a-hoop about her next project - starring in Harvey Weinstein's Viking-era epic, Outlander, with Jim Caviezel - she likes to give the impression of being the girl next door. It is not, entirely, a façade. She really does shop at Homebase. And she really doesn't think she is famous.
"I could ask 100 people in here if they knew who I was," she says. "I bet you no one would know."
But this is only half the story. For as long as she has been worthy of public interest, Myles has been both terrified and fascinated by her own press (she has been known to keep a few, choice cuttings in her handbag). And her defensiveness about her public persona has only increased as her relationship with the current darling of British television, David Tennant, has developed.
"Hmm ... I'm conscious of the fact that I don't do many interviews," she explains. "So, yes, I do keep hold of the things that are written about me. There is stuff that's invited and there's stuff that's not. I've chosen not to talk about my really private life to the press - I've never invited a huge amount of attention. So, there are no paps waiting outside my house. I think, once you start revealing the private stuff, you're essentially fair game."
What is at the basis of these fears about press intrusion is not quite clear. Myles has never been a serious target for the tabloids, despite a few gossip-worthy relationships in her early twenties, including the actors Damian Lewis and (to much tut-tutting in the gallery) Charles Dance. Compared with the other Britpackers of her generation - like her friends Sienna Miller and Keira Knightley - she has been left well alone.
"I can't quite explain it," says Myles. "But when journalists ask me about the really private stuff in my life - like my relationships - I feel my soul and my guts tightening, and I plead with them, 'Don't make me do this!' And it's not as if I can't understand why they're asking. It's probably quite interesting to some people that Doctor Who is seeing Lady Penelope. But just as I respect people's right to ask, they must respect my right not to answer."
Despite her stated reticence, Myles is in good spirits tonight, and effusive. She is, she reveals, "stupidly" in love with Tennant (who she met, a little over a year ago, as she played Madame de Pompadour to his Doctor Who). In fact, as she whiles away months of filming in Nova Scotia on Outlander, she will keep a Doctor Who figurine with her for company.
"I make no apology," she giggles. "I'm pretty excited about the fact that my boyfriend has an action doll. How cool is that? Now, all I'm waiting for is for the Doctor Who people to make a Madame de Pompadour doll so I can do a bit of Barbie and Ken action with them ... You know what I'm talking about."
This kind of talk would certainly have raised an eyebrow around the dinner table in Isleworth, south-west London, where Myles grew up. Myles finds it amusing how much is made of the fact that her father is a vicar (so, it emerges, is Tennant's), because, when you meet him, the Reverend Peter Myles is a liberal soul. But his daughter's life has, necessarily, been shaped by a few key C of E values, of which "industry" would seem to be the most prominent.
Since Myles left home, her parents have f split up. But they still figure strongly in her life. Sex scenes, for instance, give Myles pause ("I'm thinking, my Mum's watching this"), and she is desperate for me not to mention the fact that she has started smoking again ("Mum thinks I've given up").
Just as influential upon Myles, though, were her school experiences. She was a studious soul in her late teens, winning a conditional place at Cambridge to read Philosophy from what she describes as a "bog standard State school". But she was not, it seems, particularly happy.
"I wasn't Billy No-Mates, but I wasn't really popular after boys came on the scene," says Myles. "Without sounding up my own arse, I think I was a threat to some of the girls ... But I wasn't really interested in any of those sweaty, disgusting boys at that time in my life anyway. I was too busy having a crush on my drama teacher and Hugh Grant.
"All the other girls had pictures of boy bands on their walls. But I wasn't like that. My first love was with Christopher Dean, out of Torvill and Dean. I don't know what that says about me. Probably that I like men in Lycra. But I quite fancied a bit of glamour. And I definitely wanted to get out of the suburbs."
Having been spotted by the Oscar-winning screenwriter and actor Julian Fellowes in a school play at the age of 16, she had her ticket out of Isleworth. But, although Myles has had many highs in her years in the business - of which, sharing a bed with Johnny Depp in From Hell ranks as one of the most vertiginous - she has also felt the lows. One of those nadirs came at a moment that should have been her greatest triumph, the filming of Terry Zwigoff's Art School Confidential, with John Malkovich, Anjelica Huston and Max Minghella, in Los Angeles.
"It's hard to explain, but I was so terrified that it was all too good," she reveals. "I have this tendency to destroy stuff that I'm not worthy of. I didn't love it, like I should have done. I never went out. I just stayed in my hotel room eating room service and put on about a stone.
"I think part of it was I realised I was just about to be filmed naked. Most other girls, I think, would have gone to the gym and got themselves in shape. I did the complete opposite. I didn't want to face it. So I put on a protective layer."
Myles has had no similar problems with her weight since filming Art School Confidential, and she is, now, evidently more confident about her body. Not only has she been investigating vampire sex in BBC's Dracula, but she also says that, "because it's about voyeurism, the odd cheeky bit slips out" in Hallam Foe.
"I'm about a size eight UK now," she says. "In fact, my agent got on to me about losing some weight a while back, and I said, 'Dude, I'm not going to get laid if I lose any more weight!' Men don't fancy skinny birds. You know, I'm in shape, I keep reasonably toned, but I've got a bit of jingle-jangle. And men like that."
Myles seems comfortable in her own skin now - happy about her life and her man - and sanguine about her career. I mention to her that, although she has been landing enviable parts for the better part of a decade, she has often been the redeeming factor in some productions that have, let's say, been unenthusiastically received by the fourth estate.
"Oh God, I know," says Myles, grinning. "But because I've been doing this for a while now, I'm a bit more confident that it's not all luck. You can't wing it for 10 years. But, you know, I've never had a hit. I daren't tell anyone though, or they'll never use me again."
With big-budget epics like Outlander on the horizon, Myles can afford a laugh at her own expense. And, she says, a little more confidence in her acting career has led to less navel-gazing in her private life.
"I'm a bit more interested in looking out now," she says. "You can get a bit bored of finding out about yourself. I know nothing about politics, for instance. There's nothing that's stopped me picking up a newspaper in the past, and it's something I really should start to do."
It is hard to congratulate an intelligent woman - who could have been an MA (Cantab) in Philosophy by now - for picking up a newspaper. But Myles is, at least, honest about her shortcomings. Whenever she gets on to uncertain ground, she either retreats entirely - "Sorry, I actually know nothing about that" - or falls back on the pretty girl's last resort, and smiles herself winningly out of the situation.
But if she wishes to deliver a credible performance as a femme serieuse, she will have to work harder on concealing her inner luvvie. Throughout our interview, she drops the names of her showbiz mates - Keira and Orlando and Dawn French and the rest. They are, naturally, all "really nice", "just lovely", "wicked", and so on and so on.
Myles, then, is nothing if not enigmatic: a homey girl with a wild streak; a vicar's daughter with a turn of phrase that might make Gordon Ramsay blush; and a leading lady who wants the big parts, but not the trimmings of fame. It is this counterpoint of paradoxes, you suspect, that makes Myles interesting to watch, and the reason casting directors return to her again and again. She is not just a pretty face. And, when the inevitable big hit happens, she will enjoy the sensation that she has won, not bought, her fame.
"I'll never be a celebrity," she says. "What does that word mean anyway? I know so many acting careers that are deliberately kickstarted by a publicist placing a bit of rubbish in a newspaper. And I don't want that. If someone recognises me, I want it to be because they've seen me in something, not because they have seen me at something."
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