Jamie Harrison is in the middle of the technical rehearsal for the new show for which the co-founder of Vox Motus Theatre company has the wonderful job title of puppet and illusion designer.

As a member of the Magic Circle, Harrison has frequently applied his skills on such Vox Motus shows as Slick and The Infamous Brothers Davenport, as well as on the National Theatre of Scotland's version of Peter Pan. While all these were ambitiously realised large-scale works, the new musical stage version of Roald Dahl's fantastical novel, Charlie and the Chocolate Factory, is something else again.

Set to open in the heart of London's west end, the show is an international co-production between James Bond director Sam Mendes's Neal Street Productions, Warner Brothers Theatre Ventures and Langley Park Pictures. It stars Douglas Hodge as Willy Wonka, the eccentric owner of a chocolate factory who hides five golden tickets in random bars which will change the lives of the children who find them forever.

This will be the first time the story has been brought to life onstage. Mendes and co have not only enlisted the services of Harrison from Scotland's theatre scene, but commissioned leading Scottish playwright David Greig to write the book, with music and lyrics by Marc Shaiman and Scott Wittman.

One of Harrison's main responsibilities will be to bring Willy Wonka's slightly creepy helpers, the Oompah Loompahs, to life. Exactly how he does this he can't reveal. Given that the show's technical rehearsal which he's in the thick of is scheduled to last a mammoth five weeks, one should probably expect something spectacular.

"It's an organic process" is all he'll say.

Harrison says he owes his tenure on Charlie and the Chocolate Factory to Greig. It was Greig who penned the NTS version of Peter Pan, for which Harrison worked on the show's illusions, with particular focus on bringing Tinkerbell to life. Harrison's concept was one of the show's successes, and Greig suggested his name to Mendes and the myriad producers behind Charlie and the Chocolate Factory. Harrison worked on two development weeks in London, where representatives of both Warner Brothers and the Dahl estate were in attendance. "Then I got a phone call," Harrison remembers, "and was told 'we'd like to firm up our commitment to you as one of the creative team', and that was that."

Suggest to Harrison that Charlie and the Chocolate Factory is the biggest thing he's done, and he's not initially convinced. "Well, it depends on how you look at it, " he says before pausing a moment. "Yes, it is," he reconsiders. "Everyone here has won Olivier awards and all sorts of other awards, so the first few days were really quite terrifying. There are departments working on this show that I've never discovered before. There's a wig department, and an automation department, which is really important to the show, but in terms of resources I've never seen anything like it."

Harrison first became interested in all things magical when, as a child, he damaged his knee badly enough to be confined indoors. "One of my friend's mums bought me a magic set," he remembers, "and I practised and practised with it. Then I went to see a magician called Martin Duffy, who has been active on the circuit in the north-east of England for more than 20 years, and at the end of the show showed him some tricks."

Such precocity paid off, and the next thing Harrison knew he was taking a phone call from ITV children's show, Gimme Five. He went on, performed live, and "got the bug". By the time he was 14, he was performing his magic act at children's parties, and, aged 17, was contracted to tour a huge hotel chain in Asia for four months.

"The first two months were great," he says. "I spent a lot of time in Thailand, but after four months I was tired of travelling."

He was also becoming aware of some of the limitations of his chosen artform in terms of other ideas he was waking up to.

"Some of the best magic can be political," he says, "but most magic doesn't do that. I had things I wanted to say. I wanted to work with other people, and I wanted to do things that were important. I still love magic. At the highest level it can be utterly transcendent, but theatre was where I wanted to be."

He went to drama school where he met Candice Edmunds, and the idea for Vox Motus was born. Since then, the company has developed into one of the most stylistically inventive company's around. "We wanted to engage with theatre as a three-dimensional space," Harrison says of the Vox Motus aesthetic, "and do things that you can't do on television or in film. We want to explore that space, and do things with it, like turn a shed into all these different things. We can draw on magic, illusion or whatever it takes to make that happen."

He recently spent some time observing iconic Canadian theatre director Robert Lepage rehearsing with his Ex Machina company. As has been seen whenever he's brought his work to Scotland, Lepage is himself a master of illusion who works on a grand scale. Harrison was particularly impressed with the fact that the company would rehearse with a full set and technical support from day one.

"That's something Candice and I are working towards in the long term," he says. "The benefits of working like that are just enormous."

In the meantime, Harrison has Charlie and the Chocolate Factory to contend with.

"It's a visual feast," Harrison promises of the new production, "but it's the narrative that makes it. It's a story about a young boy who has nothing but love in his life, and through his own virtue he inherits his dream.

"But it's a funny thing, just talking to people about it, it splits the audience who they project themselves onto.

"Some project themselves onto Charlie, and there's some who empathise more with Wonka. But with these two beautiful characters, it's hard not to fall in love with them both."

Charlie and the Chocolate Factory, Theatre Royal, Drury Lane, London, previews from May 16.Visit www.CharlieandtheChocolate Factory.com.