NO sooner had Louise Jameson waved her Fairy Godmother magic wand for the final time in Cinderella at the Tunbridge Wells Assembly Hall Theatre on Sunday, than she began rehearsals for The Mousetrap the very next day.

"We've got two weeks of rehearsals and then we open in Nottingham on January 19," says Louise, who has been enjoying the chance to walk from home to work during the pantomime run. "It was only my fourth panto. I love Christmas, I love my family, and I'll only do panto if it's close to my home."

The Londoner will be playing Mrs Boyle in the 2016 leg of the record-breaking 60th anniversary tour of Agatha Christie’s The Mousetrap, whose 25 venues will include the Grand Opera House in York from February 22 to 27.

"I thought about doing something special for my 65th birthday in 2016," says Louise, whose birthday falls on April 20. "Just how did I get to be 65? The same way The Mousetrap has run for nearly that length of time I suppose; just second by second time has ticked away; we’ve both lasted this long, and so we’ll be celebrating together. That’s quite special.”

Louise has enjoyed long-running roles as Leela, companion to Tom Baker’s Doctor in Doctor Who; Susan Young in Bergerac; Eleanor Glasson in Doc Martin and Rosa di Marco in EastEnders. Now she has an eight-month contract in The Mousetrap, her longest ever touring engagement, surpassing a five-month stint with the Royal Shakespeare Company.

"It will be my first Mousetrap. It's a show that's been called 'National Service for actors', but I haven't done it before," she says as she prepares to play Mrs Boyle, one of the guests at the Monkswell Manor guest house in the deepest, bleakest wintertime. "She's very uptight, very grumpy and completely opposite to the characters I normally play. I hope they've cast me as Mrs Boyle because they see me as versatile!

"She doesn't acknowledge how she is; she's in self-denial, but it would be too easy just to play her as being grumpy. Every character has a secret, rather than just being two-dimensional, which is why Agatha Christie is such a great writer.

"I think Mrs Boyle has had a difficult life and a guilty life, but one where it's always someone else's fault and she doesn't really take responsibility for her actions."

Consequently, Louise feels empathy for Mrs Boyle, instead of sympathy. "She's not very lovable, but because I've looked for the reasons why she is how she is, then the empathy can be there. Looking at her, I can be very judgemental, but whoever you're playing, you have to be able to touch that character somewhere.

"It happens organically in rehearsals once the lines are learnt and they're in your muscle memory, not just your brain, and you somehow find you know this person. Mind you, I don't think Mrs Boyle likes herself."

Louise professes to not enjoying reading whodunnits through a lack of patience. "I just get carried forward, thinking, 'oh just tell me who's done it', but watching them is different," she says.

To prove the point, she has seen The Mousetrap at its London home at the St Martin's Theatre three times. "The first time, I saw it without knowing the plot, so the twist at the end was amazing. The second time, I found it much funnier. There were some fantastically differently interpreted characters too, which was just as truthful," she says.

"The third time, I was watching because I'm about to do the show. How was Mrs Boyle?! She was very good. I did a little publicity photo with Audrey Palmer, who's playing the role there, and she sweetly left me a note with good wishes. She even let me use her dressing room to get ready for the photo."

Louise has her own theory as to why The Mousetrap is such an unbroken success story. "When it went into the Guinness Book Of Records as the world's longest-running show, it became one of those To Do things, a show that London tourists put on their list," she says.

"But it's also the Christie factor. As soon as you see it's written by Agatha Christie, people want to see it because they love a thriller. There are aficionados who want to work out what's happening and those who just love theatre, and there's also a big crossover with Doctor Who, which also requires a slightly off-the-wall brain."

After spending her 65th birthday on tour in The Mousetrap, how might Louise wish to mark her 66th? "Do you know, I've never done a big major movie; I've done loads of little ones and lots of shorts, but I would love to be in a great big blockbuster," she says. "Even if it was only a small part, it would be a wonderful 66th birthday present."

The Mousetrap plays Grand Opera House, York, from February 22 to 27 and Harrogate Theatre from May 2 to 7. Box office: York, 0844 871 3024 or atgtickets.com/york; Harrogate, 01423 502116 or harrogatetheatre.co.uk