Jenny Rainsford lives in Camden and grew up in Watford, so how does she go about playing a mysteriously sexy French woman who drives a man crazy with her playful nature in Little Black Book?

She called on the advice of her mentor and her mum’s best friend, the supremely chic Mary Portas, of course.

The actress, it turns out, is a bit like a little black book herself, and this is just one nugget of information waiting to be discovered during our interview.

From the outside it looked like our talk would be fairly straightforward, a quick rundown of the play she is starring in at Park Theatre. But then, as we chat, I find out all sorts of surprising facts, like her mother being the famous historical fiction author Katharine McMahon, and that Jenny’s love of theatre was inspired by watching her mum and Mary leap about rehearsing for their St Albans am dram group, Company of Ten.

“It was great,” says Jenny, ”their charisma and theatricality was what gave me the bug in the first place.

”Mary is a complete inspiration and I talk to her all the time.

“When I started this project I said to her ‘I don’t know how to handle it’. She’s just a complete force of nature and doesn’t see the negative and said: ‘you can do anything’.”

Then Jenny hits me with another story. Her first acting experience was performing in Macbeth in New York for Prince Andrew and Mayor Giuliani, but just weeks after the September 11 bombings.

”It was totally messed up,” says Jenny. ”We were standing in Grand Central Station with smoke and all these missing people posters in the walls.

”I was 17 and it was my first time abroad. It was kind of horrifying, a really vivid experience and quite overwhelming.”

Fortunately it didn’t put her off acting and she went on to study English literature at Oxford and then went to RADA.

Upon graduating two years ago, she was almost immediately offered a job in About Time, the recent Richard Curtis film, and also had a small role in Ridley Scott’s blockbuster Prometheus.

”We flew up to the Isle of Skye and it showed me what money can buy in terms of filmmaking because they had 3D cameras and helicopters.

”Of course, I want to do more films, they pay the bills.”

Finally, it’s time to talk about her latest off-screen project, a French play by Jean-Claude Carriere, translated by Solvene Tiffou.

The 28-year-old says: ”Its a bit like Breakfast at Tiffany’s and very French.

”The character I play is a bit like Holly Golightly. She’s a terror and turns up in this man’s apartment and just stays. It’s a love story told in three days and you see them fall in love.

”It starts with her playing him and then it turns around and he plays her.”

She adds: ”It’s like a really, really, wonderful, racy, intense rom com.”

Jenny and co-star Gerald Kyd are the only two actors in the seven-scene play, which is an hour and ten minutes long with no interval.

Despite the intensity of the play, Jenny, who got married last month, says: ”There’s no raunchiness because it’s kind of above the sexual stuff.

”You know they have probably slept together between a couple of scenes, but their emotional intensity is so much more thrilling that the writer didn’t need to put any sex in.”

  • Little Black Book is at Park Theatre, Clifton Terrace, Finsbury Park, until January 19. Details: 020 7870 6876, parktheatre.co.uk