HARRY Potter film star Oliver Phelps is making his stage debut in the 1930s' whodunit The Case Of The Frightened Lady, on tour at the Grand Opera House, York, from July 9 to 14.

After playing George Weasley in the Potter film franchise, Phelps swaps magic for a manor-house murder in the Classic Thriller Theatre Company staging of Edgar Wallace's novel that will visit Leeds Grand Theatre too from July 23 to 28.

Phelps will be playing Sergeant Totti, having appeared in the Potter films from the age of 15, when he was cast with his twin brother James in the mischievous roles of Ron's older brothers.

In Antony Lampard's stage adaptation, Inspector Tanner is called in to investigate a ruthless murder at Mark’s Priory, the grand ancestral home of the Lebanon family, whereupon he soon discovers nothing is quite as it seems. The household is controlled by the family physician, the footmen behave more like guests than servants and the secretary, Isla, is afraid for her life. As Tanner moves closer to the heart of the mystery, he uncovers a shocking and closely guarded secret.

"I play a young detective who’s very vigilant. He’s switched on and always taking notes," says Oliver. "And he’s always watching what his superior officer, Inspector Tanner, is doing because he’s trying to learn from him."

When he read the script, set in the aristocratic Thirties, Oliver loved how the story kept him guessing right to the end. "That is the sign of a great story. There’s nothing more boring than going to see a whodunit and realising who did it early on. This play certainly doesn’t give you that," he says. "Your mind changes throughout the show as to who has committed the crime."

Oliver is enjoying his professional stage bow at the age of 32, working alongside Deborah Grant, Gray O'Brien, Denis Lill, Philip Lowrie, April Pearson, Ben Nealon and Glenn Carter in Roy Marsden's cast. "It's something I’ve not done before, which I’m really excited to be able to try. The way I see it, if you want to be taken seriously, you’ve got to be able to do theatre," he says. "I’m lucky, because the majority of the cast have already performed the show lots on tour.

"Joining the company, I thought it might be a ‘first day of school’ situation, but they were all brilliant. I know I need to prove that I can do it live in a theatre, but I love that sink-or-swim challenge and I’m sure I’ll find out there’s no better place to sink or swim than on the stage."

Oliver has no qualms about adapting to the touring life. "When I was filming the Harry Potter movies, I virtually lived in a hotel room for nine months of the year, so I know how it can be. You can just sit down and do nothing the whole time," he says. "It’s the worst when someone asks, 'What did you do?' and you say, 'I don’t know', which I have been guilty of doing before.

"So I’m really looking forward to visiting parts of the country I haven’t seen before. And I’m taking my golf clubs and my gym bag. I’ve already been exploring places to play golf."

Friends of Oliver will be attending his stage debut. "Quite a few of my pals who don’t normally go to the theatre are coming along. It will be a new experience for them, so I’m looking forward to those dates. In Leeds, a friend actually works for the theatre. Another friend has a company based in York, so people will be coming there," he says. "And then there’s Coventry. I’m from Sutton Coldfield, only 25 minutes down the road, so a few of my pals will come there."

As he settles into a theatre tour that began on May 21, Oliver reflects on the experience of appearing in the Potter films. "It’s only when you look back that you realise it really was huge. It still is." he says. "When you’re so close to it, you don’t understand the size. You think every film has a £120 million budget. I’ve since learned that isn’t the case.

"At the first premiere, Robbie Coltrane said to us, 'Guys, this is like having a Rolls Royce for your first car'. At the time I didn’t understand what he meant. I now understand it a lot more.

"My brother James and I have travelled a lot with Harry Potter: The Exhibition; it’s amazing to see people who came to that who weren’t even born when the films came out but know everything about them. When you’re filming, you don’t realise you’re part of something that has that impact."

One experience from his Potter era stands out. "It was pretty terrifying when Barack Obama’s family came for lunch in the Great Hall and the secret service were on the roof with their rifles," Oliver recalls. "You needed to have your staff pass that day."

Bill Kenwright and The Classic Thriller Theatre Company present Edgar Wallace's The Case Of The Frightened Lady at Grand Opera House, York, July 9 to 14, and Leeds Grand Theatre, July 23 to 28. Box office: York, 0844 871 3024 or at atgtickets.com/york; Leeds, 0844 848 2700 or leedsgrandtheatre.com

Charles Hutchinson