Ali Cook fishes around in the pockets of his suit jacket and hands me a pair of walnuts.
The most clean-cut, softly spoken and potentially sinister magician in the business politely asks me for a coin. I give him five pence and he makes me write my initials on the shiny silver surface with a black marker. Then with nothing more than a handkerchief, a nut cracker and a high-pitched giggle, he proceeds to make my coin vanish and reappear inside the walnut. I have no idea how he did it. I start squealing and begging for another one.
But my reaction is nothing. A trainee doctor once fainted when Cook, who won the British Sleight of Hand Championships when he was just 17, performed an illusion that apparently involved removing someone's intestines from their stomach.
"That was by far the best reaction I've ever had," he says wistfully. "It's also the most disgusting thing I've ever done, opening someone's stomach up. I made a child cry watching me swallow razor blades too. But," he says with a smile, "I don't really do kids shows.
"The walnut trick is usually done with a ring. But yours is too big for the walnut," Cook continues, eyeing the enormous piece of plastic on my finger that he later causes to vanish and reappear on the keyring in his back pocket. "I invented the walnut trick. It used to be the one I was known for in the magic world."
That's all about to change with Cook's new Edinburgh Fringe show, Pieces Of Strange, currently bringing the house down at Gilded Balloon (and so far inducing no faints). It's a brilliant hour of gross-out, head-scratching alternative magic and leftfield stand-up. Expect to see Cook read minds, make coins disappear under credit cards (the smallest yet most difficult trick in the show), magic up Colman's Mustard Powder from water, and swallow razor blades until he spews blood.
His new signature piece of strange is on a slightly larger scale than the nuts, involving a water tank, a set of chains, and a very clever 30-second escape. When we meet in London the tank is in his kitchen, having just arrived from Los Angeles, where it was crafted by the world's greatest illusion builder.
"It's based on Houdini's water torture cell," Cook explains. "But magicians don't really attempt it any more. I'm chained inside a locked water tank, unable to breathe, and then I escape. I did this trick before on TV and the first time I got stuck in there for about three minutes. I eventually managed to whack the lid off and crawl out covered in cuts. Imagine being stuck in the boot of a car that's full of water. I've had to practise eight hours a day and get over all sorts of phobias. Oh, it's horrible."
So why exactly does he do it? "I don't know any more," he laughs. "I suppose I'm trying to find something no one else has done. This trick has never been seen in Edinburgh. And it hasn't really been done anywhere in the world for 50 years." Karen Koren, artistic director of the Gilded Balloon, begged Cook not to do it because she was afraid he would drown. So far he's making it to the end of the show.
Cook, like his friends Derren Brown and Pete Firman, is a major player on the alternative magic scene though this is only his second time in Edinburgh. He has caused rings to vanish from the Royal Family's fingers and wowed parties hosted by Damien Hirst and JK Rowling. Leonardo DiCaprio ("very down to earth") and Victoria Beckham ("a real sweetheart") were apparently both "well impressed" by his sleight of hand.
"I once did the walnut trick for Fergie," he recalls. "I vanished her ring, which was valued at half a million. There was a considerable sigh of relief when it reappeared inside the walnut. I just couldn't believe she handed it to me without blinking an eye. Everyone responds the same with a good trick. It's a great leveller. I even got Carol Vorderman, and it was a trick that relied on maths."
Cook's influences are Penn and Teller and Derren Brown rather than traditional showmen like Paul Daniels and David Blaine. He doesn't really go in for all the bells and whistles and capes. "I do magic with everyday objects - IKEA Family cards and watches - and I try not to be cheesy," Cook says, adding that this is the illusionist's worst crime and one he sends up in Pieces Of Strange. "What I do is closer to stand-up but with tricks instead of jokes. It's magic without the arrogance."
Cook grew up an only child in Harrogate. "Yes, I was a geek without a girlfriend who spent all day reading magic books in bed," he says with a smile. By the time he was a teenager he was obsessed with mastering tricks, cheating at cards at school until no one would play him any more, and even conquering the famous and usually famously unopened Paul Daniels magic set. "My mother was always into the occult," he says. "She read tarot cards and crystals and had a new age shop. A couple of books about sleight of hand came into the shop and I read them cover to cover."
He remembers learning a classic "move" from the Paul Daniels magic set that allowed him to hold a ball but show both hands empty. He practised it hour after hour and once he could do it, he was hooked. I still think it's an amazing move," he says, doing it absent-mindedly with his walnuts as he goes on, hypnotically passing them from hand to hand so I look like I'm watching a very tiny game of tennis.
"I found it incredible that you could have something in your hand that no one could see. And then I got into pickpocketing and would make my mum wear my dad's blazer while she was cooking tea and pick her pockets. I found it weird and amazing that you could take a watch off someone's wrist without them knowing." Could he do that with my ring now? "It's tough," he says, "but it's doable."
In recent years, Cook has been responsible, alongside the likes of Brown and Firman, for bringing the magic show back to British TV. Dirty Tricks, a Channel 4 series in which Cook and other world magicians performed, was the first of its kind since Daniels' classic show of the Eighties and Nineties. Cook also travelled the world with Firman for a series on Sky interviewing some of their illusionist heroes. "Juan Tamares, a Spanish guy, is like the Woody Allen of magicians," he says. "He did a trick that is so simple, but is the most impressive I've ever seen. It was just thinking of a card and he knew what it was. A classic trick but we just couldn't figure it out. I still don't know. It's always the simplest thing. If someone could make a coin disintegrate in front of your eyes, that would be the best trick in the world."
None of this would have happened without Jerry Sadowitz. It was when Cook met Glasgow's top-hatted trickster that things started to really take off for him. I'm guessing it's also where he developed his humour. Suffice to say, on the night I was at his show, a heckler at the back protested at one point "come on man, that's just sick".
"I moved to London and ended up living opposite Jerry," Cook recalls. "He used to hand-write this really offensive underground zine where he would slag off loads of magicians but also give you really good tricks. I subscribed to it, realised he lived over the road, and eventually went over and knocked on the door. I ended up being the guest magician on his TV show."
Magicians remain a rare breed. But the surge in new cabaret and music hall means that magic is enjoying something of a renaissance too. Still, according to Cook it will always be the niche dark art that not many people can be bothered to master. "It's really difficult to learn," he shrugs. "You have to be mildly autistic and incredibly geeky to do the same thing over and over again for hours, weeks, years, until you've mastered it." He laughs and pops his walnuts back in his pocket. "I don't get out much."
Pieces Of Strange, Gilded Balloon Teviot, until 30 August, 9.45pm
• This article was first published in Scotland on Sunday, August 15, 2010