Wannabe singers in some of London’s mushrooming karaoke pubs did a double take when they spotted former pop sensation Billie Piper in their midst.

The chart-topper was not bent of a singing session; she was researching for her role in The Miller’s Tale as Alison, the talented young wife of a pub landlord whose twin obsessions are karaoke – and her.

"I used to sing karaoke all the time, including ‘La Bamba’ with my dad, which was always hysterical," she laughs. "But I’d not done it for ages, so I dragged my friends around all these pubs to get a feel of what it’s like.

Fans of Piper – who had hits including ‘Because We Want To’ and ‘Day and Night – may be in for a shock when they see her as Alison, giving her all at the karaoke machine. Thanks to special training from Fame Academy’s Carrie Grant, her voice has changed.

"I didn’t want to go on screen and do something everybody that already knew about", explains the twenty year old. "It would have been hard to get into character if I was singing with a voice I had sung with forever."

"That’s why I got in touch with Carrie. She’s an amazing woman, so special, and working with her was a wonderful experience; she can sing with so many different voices. She helped me change my technique, showing me different ways of playing my voice in my throat or stomach.

"I wanted Alison to have a voice that belonged to her and nobody else."

Making her acting debut is important for Piper. "What people don’t really know is that I started out acting", she points out. "It’s a really big deal to me."

"I left home in Swindon to come to Sylvia Young’s theatre school when I was 12 be I’d applied for a scholarship – I needed to act 24/7, all week, just throw myself into it. At home, just one class a week just wasn’t really doing it for me.

"Then the pop career came along and although at the time a realised it would take away from the acting, I felt it could open a lot of doors for me, which I think it has."

But it is open windows, rather than doors, that most people know from Chaucer’s original ‘Miller’s Tale’ and writer Peter Bowker reinvents the famous scene where Alison tricks a young suitor into kissing her bare behind.

"I was quite daunted by that scene", Piper admits. But John McKay, the director, drew a storyboard of how the whole scene would be shot and how it would look. He really wanted me to feel at ease. So you don’t see my arse full on," she laughs. "It’s poor Kenny Doughty who plays Danny who got the whole shebang – but that wont be seen!"

Piper also has to perform steamy sex scenes with ‘Bloody Sunday’ star James Nesbitt. "As a viewer you always want to ask, ‘Was it weird, did they get turned on, did they crew get turned on, what does your boyfriend feel about it?," she admits with a grin.

"But when you’re doing it, you’ve got these pieces of tape round your breasts and the ugliest tanned thong on and all the lighting and sound. It’s just not sexy – which makes it easy to play sexy, and just go for it in the mindset of the character. I can imagine that in those situations, if you don’t suspend reality it can really mess with your head, because it’s not real," Piper explains.

Which is why Piper is relieved that her husband is ‘au fait’ with the entertainment business. "My husband understands that it’s my job," she says simply. That’s the good thing about being married to somebody who understands the technicalities.

"Having been married for two years I’m more domesticated now and I love it," Piper insists. "I know it sounds a bit of a cliché, but when you come home and just do some jobs around the house it does just bring you back to earth because after filming you’re so hyper.

"You have to come back down, otherwise you don’t sleep, you grind your teeth and just burn yourself out!"

Piper douses speculation that she is about to return to her pop career, insisting that the whirlwind of early-morning plane journeys and endless interviews is one she is glad to have turned her back on.

"It was just too fast-paced," she says. "That’s one of the reasons I decided to have a break. If I carried on I would have missed out on so much real life and I’m so happy acting. It gives me the time and freedom I need in life. When I finish a day’s work I can still get time at home to make some dinner, watch a bit of TV, have a cup of tea in bed.

"I love cooking – I hated it before I met my husband, he taught me all I know about the kitchen. I love making pasta sauces, stews and baking – although I’m still working on that!

"I love hanging out with our dogs, just being part of proper things and it’s these things that help me act because, if you can’t observe real life situations, then how can you go out there and try and observe someone else?"