"Oh, sorry," she says with a giggle. And then, in explanation: "Night-shoots, Doctor Who, and I'm so very tired. My voice is all croaky, and my eyes are in my shoes. Can you tell?"
For the past couple of weeks, Piper has been going to work when most other people are going to bed. She is resuming her role as Rose Tyler, the effervescent sidekick of Doctor Who, a character now being played by David Tennant following Christopher Eccleston's rather abrupt departure at the end of the first series.
Despite much tabloid speculation that Piper herself was also quitting the show - for movies, for Hollywood, for wraparound superstardom - the truth is that she is staying precisely where she is. For now, at least.
"Well, I've not heard any rumours of me being killed off," she says. "So as far as I'm aware, I'm around for the entire second series." And after that? "Well, we'll see."
The night-shoots, she admits, are taking their toll, not just on her body but, it seems, her public profile as well. Eighteen months ago, Piper filmed a British horror flick called Spirit Trap. It has been collecting dust on the shelves ever since - and, many suggest, rightly so - but in the light of its leading actress's blossoming profile, it has suddenly secured a release date. What's more, the producers wanted to arrange a red carpet premiere, with Piper's presence sure to secure significant media interest. But rumours abounded that Piper had seen the finished product and was appalled at its awfulness, so appalled that she wanted nothing more to do with it. All such accusations were summarily denied, with Piper's lack of support blamed on pressure from the Doctor Who schedule. There were apologies all round.
"Billie has had a lot of commitments," said a source close to the film. "But that's cold comfort to her co-stars, crew and director. If she can't make the premiere, then there's no point."
And so there was no premiere. But thenSpirit Trap wasn't worthy of one in the first place, largely because - Piper's bright performance aside - the film is a clunking piece of haunted-house nonsense that singularly fails to frighten. One might wonder why she did it in the first place.
"Because I love horror films, that's why," she says. "When I was younger, too young to go out on the lash, I would watch horror films and scare myself out of my wits instead. So when the opportunity came to do my own one, I could hardly resist it."
Perhaps because she seems so naturally disposed to being polite, Piper insists that her failure to fully support the film's release was not because she hated it, but because, genuinely, she was too busy. As she claims this now, she begins to beseech.
"Look, I love it, I really do, and I fully support it. Actually, all that tabloid nonsense has made me really angry because I've upset a lot of good friends I made on that film, but then, you know what? I can't be arsed to try and persuade everybody how I really feel about it because that just takes more energy than I've got."
She confesses to having not read any of the reviews and, as diplomatically as I can, I suggest she keeps it that way. "Oh, but I have heard that they aren't particularly great, right?" Right. "Oh well, what can you do? I will admit that, yes, the script did have moments of weakness, but I had a lot of fun filming it. And anyway, as an actor, you want to work, and you learn so much more from being on a film set than you do in drama school, so this was really insightful for me. It was educational, and I don't regret it at all."
She stops to fiddle with her cigarettes, and then takes a long suck on her carton of orange juice. "The way I look at it is this: sometimes you do bad things and sometimes you do good things. Sometimes people respond well to your work, and sometimes they won't. But when opportunity comes along this business, you have to take it. You take it, and you learn from it and you grow." Spoken like an old pro.
Billie Piper was born in Swindon on 22 September 1982. Her parents initially christened her Leanne but, three weeks later, had an abrupt change of heart and settled on Billie. By the time she was 11 she was at stage school and, after being spotted in a TV advert, was offered a recording contract at 15, seemingly irrespective of whether or not she could sing.
Billie looked, back then, much as she does today: like a Japanese manga cartoon made flesh, all eyes and teeth and supersonic smile. In 1998, she became the youngest ever female solo artist to top the UK singles chart with "Because We Want To", an anthem for tweenies desperate to stay up late and overdose on sugar. But within a year of the release of her debut album, Honey To The B, her fanbase had turned on her. At the 1999 Smash Hits Poll Winners Party, at which she was named Best Female Star, she was relentlessly booed by jealous fans of Richie Neville, member of the boy band 5ive whom she was then dating. In 2000, her second album, Walk Of Life, was also her last.
"I had an amazing time, but it was also pretty horrible," she says. "That's why I was so happy to walk away, to go off and try to reinvent myself. I never really wanted to be a singer in the first place. I just wanted to act."
And so she went to Los Angeles to study under acting coach Larry Moss, before returning to the UK and attending countless auditions, often without success. But then, in 2001, her comeback accelerated when she fell in love with and subsequently married Chris Evans, the multimillionaire radio and TV star who is 16 years her senior. Piper's public life then became a series of paparazzi shots: daytime drinking at the local pub; drinking the night away on somebody's yacht; drinking throughout endless beach holidays. "That time taught me a very valuable lesson about fame," she says. "In that, effectively, I've become completely indifferent to it. I love my job and I understand its requirements, but I'm not interested in having a public life."
In 2003 she started passing auditions, and subsequently appeared in a modern-day re-telling of The Canterbury Tales on BBC 1, and the hard-hitting drama Bella and the Boys on BBC 2 the following year. She the starred alongside Orlando Bloom in the film The Calcium Kid, and promptly thereafter landed the Beeb's sci-fi time-traveller gig. By this stage, her marriage to Evans was over, but the girl whose 15 minutes had long since expired was given another bite of the cherry. Public opinion had gone full circle. Now, everybody seemed to love her.
"I have to say I'm feeling pretty fearless at the moment," she says. "I just feel like I have nothing to lose. I've got six years' experience of this industry under my belt, so now I'm just going to go for it."
Privately, meanwhile, she is learning how to live life in the spotlight. Much to the disappointment of the press, she says, she and Evans have remained friends since their divorce. Billie is currently dating 27-year-old Amadu Sowe, her publicist when she was still a singer, but her personal life is something she now avoids discussing. "Only because I don't want my life encroaching on his any more than it has to. With Chris, things did get a bit crazy with all the press attention, and I'm not particularly keen on crazy."
At 22 years old, then, Billie Piper is virtually a showbiz veteran, wise beyond her years and, despite the amassed experience, still very much a beginner. Irrespective of wealth and fame, she remains surprisingly down-to-earth, and if she is guilty of being the demanding diva her job description effectively encourages, then she conceals it rather well. In many ways, she is a typical 22-year-old, one who likes a drink, a smoke and a night out with the girls. She says she loves her north London neighbourhood, and that she has a set of very dear friends, the kind she has coveted since childhood. Consequently, Hollywood holds little allure for her right now, and the last thing she wants to do is run before she can walk.
"I'm really happy with my life at the moment. And anyway, I can't imagine things getting better than they are right now." She smiles, and her teeth smile right along with her.
'Spirit Trap' is on general release. 'Doctor Who' returns to the BBC in the springReuse content