When Daniel Clarkson and Jefferson Turner first came up with the idea of staging all the Harry Potter books in just one hour, they took an early prototype to a primary school to test it out.

"There's a bit where Dan has to slap me round the face and say 'I hate you'," says Turner. "He's being Snape, and each character only has a second or two to get across their emotions. A week later we got called back in to the school for a special assembly where we had to ask the children to stop doing it to each other in the playground."

Now the show that spawned a whole new playground craze - we'll call it Harry Slapping - is coming to Brighton on its first national tour, and adults are more than welcome, too. In fact 20-somethings made up the biggest proportion of the audience when Potted Potter sold out the Edinburgh Fringe this summer. Having grown up with JK Rowling's tales of a boy wizard discovering his destiny, they are now turning this fond parody into a cult hit.

"It's a bit similar to agit-prop, in that all you need to change character is a wig or a hat or a pair of glasses," says Turner. "It all looks very cheap which is the sort of look we wanted - partly because Warner Brothers warned us off about replicating any images from the films. We're on a very slippery tightrope with their lawyers. They've even tried to argue that they own Harry Potter's glasses."

A professional storytelling duo, Clarkson and Turner started out adapting fairytales in Covent Garden before landing a slot on Blue Peter condensing the adventures of Artemis Fowl, Tracy Beaker, Molly Moon and the like down to one tightly choreographed minute. Then, in 2005, a London bookshop asked if they could perform a similar feat to mark the release of the sixth Harry Potter book, and the result developed into an hour-long show incorporating an interactive Quidditch match with broomsticks and everything.

"Dan was already a massive fan," says Turner. "I had to read all six books in two and a half weeks. We had to strip them to the bare bones and because I wasn't so married to the material I could quite easily throw 100 pages out the window and watch Dan cry as I did so. Having said that, we were more than happy to lose 300 pages of plot just to make room for a silly hat or beard."

The premise of Potted Potter is that Clarkson has blown the show's entire budget on creating the dragon for book four. So while Turner plays Harry Potter, Clarkson must play everyone else.

As Turner points out, this makes things very interesting when they come to portray the blossoming attraction between Ron and Hermione.

"My absolute favourite is Professor Snape," he says. "For some reason he's become slightly Eastern European - Dan obviously has many voices to do and Snape ended up with this one. We're going at breakneck speed so I think we're allowed to make mistakes. In the past we've got our OWLS and our NEWTS mixed up, the Triwizard events in the wrong order, and we did actually do three shows in a row where Dan called Buckbeak Bucklebeak for which he should've been shot, obviously.

"If we do make a mistake you can guarantee a child in the audience will put their hand up, not quite understanding the difference between the classroom and the theatre. We generally just stop and see what they want."

After Christmas Clarkson and Turner will rewrite the show to incorporate the seventh and final book, Harry Potter And The Deathly Hallows, which was released in July. For now they're kindly assuming that many six year olds will still be making their way through it, and promising to give nothing away. Instead they indulge in random speculation and a show-stopping rendition of Gloria Gaynor's I Will Survive in which the characters compete over who will be killed off in the seventh book.

"Voldemort's got a very interesting singing voice," says Turner. "It sounds surprisingly like a teenage boy's breaking voice, ranging from the very deep to the extremely high. We seem to have transformed Voldemort into a bit of a camp icon without realising it."

  • Starts 4pm and 7.30pm, tickets £8/£6. Call 01273 647100.