Magic shouldn’t be about watching a sales pitch,” says Stuart MacLeod. “No one reacts any more to that old routine of, ‘Here’s a box, here’s a bit of rope, you’re about to be amazed’.”

“We like magic that taps into people’s fears and phobias,” adds Barry Jones, the other half of twisted magic act Barry and Stuart. “Stuff that can inject a bit of meaning, draw you in and really make you feel something.”

So it is, that after tapas in an Edinburgh restaurant, the double act — who provoked the ire of a traditionalist bishop who wanted to crucify them — begin performing an impromptu trick at the table.

MacLeod produces a pack of sewing needles from his shirt pocket as he starts reciting the rhyme, “Cross my heart, hope to die, stick a needle in my eye”.

It’s not until Jones starts moving the needle near his left eye that people at neighbouring tables start to look over. When blood dribbles from his nose, a waitress almost drops her tray. A few seconds later, Jones pulls the needle slowly out of his right eye and sits back to take in the looks of horror all around him.

Barry and Stuart’s macabre and vaudevillian magic has been earning them a cult following, spurred on when their Channel 4 series, Tricks from the Bible, was nominated for a Scottish Bafta in 2006.

Their 2005 TV show, The Magic of Jesus, showed the pair creating illusions inspired by the New Testament. It was a typically inventive blend of horror and old-fashioned trickery, where a headless body appeared to come back to life, water was transformed into wine and a blind person could temporarily see.

“If it’s done well, good magic should shatter your world and make your brain melt,” says Jones, 28, with a mock-deranged look in his eye. He and MacLeod, who met as teenagers at a magic club in Aberdeenshire, say their inspiration comes from 19th-century magic, Tim Burton films, nursery rhymes and 1980s toys and games. The duo describe their creepy blend of sorcery and classic sleight-of-hand showmanship as “the anti-Paul Daniels”, where they design tricks that bring back the wow factor they believe had gone missing from modern magic.

In one street performance in London, they replaced the traditional sequinned magician’s assistant with a tiny African boy. Masquerading as charity workers raising money for starving children, the jaws of passers-by dropped when they magically produced the barefoot lad from behind a black cloth. “People are so used to seeing magic tricks now, they’ve lost their impact,” says Jones. “We want to bring back the element of surprise — and scare people too.”

Although Jones and MacLeod, 26, have been performing together since they were teenagers and their 2003 TV series, Magick, has been broadcast in Australia and America, this is their first year on the Fringe. Originally from Peterhead (MacLeod) and Portlethen (Jones), the pair now live in London but are staying with family in Edinburgh during their festival run.

Their nightly stage show, Part-Time Warlocks, channels the gothic geekiness that has become their trademark. Jones throws his fist through MacLeod’s stomach, then performs voodoo black magic on a nervous-looking member of the audience. Rubik’s cubes fix themselves spontaneously, bowling balls appear to drop out of shirt sleeves and, in a gory storytelling section, a boy with a tongue possessed by the devil swallows a handful of razor blades.

The water into wine trick also reappears and, in a slick hour-long montage of card tricks, spooky-sounding theremins and warm, self-deprecating banter, they have produced a genuinely creative show without a velvet bow-tie in sight.

“Without magicians like David Copperfield or Paul Daniels, there would be no place for people like us,” shrugs Jones, who used to love watching both men on TV growing up. After they had perfected the basics, Barry and Stuart’s cheeky sense of humour crept in to the act mostly by accident, as they hated watching magicians who took themselves too seriously.

“When we look up at the crowd, it’s amazing to see intense fear across their faces,” says MacLeod. “Then a few minutes later they’re laughing or looking confused. Basically any facial expression is good, as long as it’s not utter disappointment.”

Barry and Stuart: Part-Time Warlocks is at the Underbelly until August 24, www.edfringe.com