Billie Piper has made her stage debut in a love triangle drama - with her real-life boyfriend as one of her co-stars.

This exclusive picture shows Piper and Laurence Fox treading the boards together in Treats, by award- winning playwright Christopher Hampton.

The play, which transfers to the West End on 28 February, bears more than a passing resemblance to real-life events surrounding Piper and Fox. The pair grew close while rehearsing and are said to have ditched long-term partners to be together.

Last night, theatre-goers declared Piper's performance a triumph - after giving her a round of applause just for walking on stage.

"It was fantastic - Billie's acting was amazing," said drama student Elizabeth Barber, 17, who lives near Bracknell.

Treats opens with journalist Ann (Piper) and her earnest new boyfriend Patrick (Fox) being disturbed by her furious ex, Dave (Kris Marshall, who played Nick Harper in the BBC TV series My Family).

As the story unfolds, Ann has to choose between the kind but dull Patrick and the intoxicating but cruel Dave. The audience is left guessing to the end whether Ann will follow her head or her heart.

In real-life Piper, 24, seems to have followed her heart, reportedly breaking up with Amadu Sowe, her lawyer boyfriend of two years, after falling for Fox last month.

At the same time Fox, 28, son of James Fox and cousin of Emilia, walked out on his girlfriend of six years. But he and Piper left their passion at the stage door of the Theatre Royal in Windsor.

"You wouldn't have known they were going out because their acting was so good," said student Lucy Saxton, from Maidenhead. "But I did notice they went off hand-inhand-together at the end of the final curtain call. I thought she was a bit nervous at first but it got much better. I really enjoyed it."

Teacher Laura Johnson, 26, from Taplow, Berks, said: "It's a credit to her that you couldn't tell they were together. She had great chemistry with Kris too. I'm not sure whether her character would have ended up with either of them ultimately, but she's most definitely got the right man in real life.

"They suit each other well. She comes across as such a lovely person and he seems a nice guy too.

"On stage she plays a really bitchy character. It's very different from the roles she has played on TV and she pulled it off well."

Engineer Ross Wilson, 27, from Flackwell Heath, Bucks, admitted he had booked tickets purely because of the leading lady.

"My only complaint is her part was smaller than the boys' roles. I'd like to see her in bigger things and I think that's inevitable after tonight."