Peter Ross: YouTube sensation hits streets to prove he's the wheel deal

Meeting him in the flesh (and blood) is an odd sensation, a bit like plunging through the computer monitor and being introduced to an entity composed of pixels and bytes. MacAskill, after all, is that curious breed of contemporary celebrity – an internet sensation.

Footage of him performing stunts on the streets of Edinburgh was posted on YouTube last month and has since been played five million times. And little wonder. The five-minute film, shot by his flatmate, opens with MacAskill riding his heavily modified mountain bike along the top of some spiked railings in Marchmont and also includes a clip of him performing a back flip off a tree in the Meadows. "What you don't see is the hours of attempts that it took me beforehand and me sprachlin' over the handlebars," he laughs.

In March, MacAskill was working as a bike mechanic, more concerned with inner tubes than YouTube, but since his online ascendancy he's been asked to appear on US chat shows, endorse clothing brands and appear in a video by the rock band Doves. At just 23, he's Danny, champion of the worldwide web.

"Jings, look at his skint knees!" exclaims one woman who has put down her messages to watch the show. "Ah ken!" hoots her pal, goggling at the knees in question.

MacAskill is wearing three-quarter-length shorts which reveal the scarlet scratches and divots from his pedals striking his shins and elsewhere. He has a metal pin in one wrist, dodgy tendons in both, and has broken his feet on several occasions. He cannot properly straighten his legs. Still, he prefers to accentuate the positive: "I've still got all my teeth and my genitals are intact, just about."

MacAskill is appearing as part of the Original Bicycle Festival within a taped-off area in Dumfries's main shopping street. The backdrop to his performance is the Mid-Steeple, a large red sandstone building where, in 1796, Robert Burns's body lay on the night before his funeral.

In a pleasing contrast with the viral, digital YouTube phenomenon, today is about old-fashioned town square entertainment. While his Barnum-ish manager Iain Withers gives an excitable commentary – "Who wants to see some carnage?" – MacAskill gives a 15-minute display.

At the climax, he jumps the bike up onto a 4ft-tall platform, an act which seems more like levitation than agility, bounces on his back wheel up a ladder made from scaffolding poles and onto a six-foot platform. From here he leaps off his pedals onto the front wheel, spins the frame of the bike around the wheel, leaps back on the pedals, then jumps off the platform, turning 360 degrees in the air and landing with all the insouciance of a cat still in possession of all nine lives and a decent pension plan. Old wifies clap, an eight-year-old girl with a blonde ponytail squeals "You rock!", and even the neds clustered on a bench are impressed enough to stop spitting, though they soon resume.

MacAskill is performing this show three times a day in small towns across Scotland in a tour set up before the internet buzz. Given his new global potential, this is the cycling equivalent of seeing the Sex Pistols at the 100 Club or Elvis pelvising on the back of a flatbed truck. MacAskill is pretty humble with it, though, signing scores of autographs for kids.

Over an alfresco lunch that seems to consist mainly of hummus and HobNobs, MacAskill explains how YouTube changed his life. "It's so funny and unexpected," he says. "I'm amazed by how mainstream it has become. Even people who have nothing to do with bikes seem to relate to it. I get e-mails saying whole school classes get shown it, and there's a guy in the States who made a physics factsheet about it."

MacAskill lives in Edinburgh and rides for around three hours each evening. He always listens to music, absorbed in a world of his own, aware of little more than the rhythm of the music and his cycling. In the past, he hasn't been particularly aware of the effect his stunts have on passers-by who witness them, but over the last few weeks he has found he often gets stopped to sign autographs, which he finds strange. "I'm pretty shy, really," he admits.

The YouTube film had such impact not just because of MacAskill's dramatic stunts but also because of the way he uses Edinburgh's street architecture. It makes viewers familiar with the city see it anew – as a huge playground of stone and steel – and this chimes precisely with the way it appears to MacAskill himself. Originally from Skye, where his father runs a museum dedicated to his ancestor, the 19th-century giant Angus MacAskill, Danny moved to the capital only three years ago and is still enchanted by the potential for stunts afforded by the urban landscape. Walking to the pub with him is a nightmare because he is forever stopping dead in the street, examining the angle of walls and making calculations in his head.

MacAskill is resistant to analysing his own inner drives, but there are glimpses of something steely inside. Some of his most complicated stunts take days of practice to perfect and are very dangerous, but he feels compelled to complete them. Anything else would be a failure. He has a touch of George Mallory about him, cycling along spiked railings simply because they are there. Edinburgh, however, may already be too small to hold him. He has had offers to work in the US and Asia, and his next film is likely to take the form of a road trip.

That's for the future, though. New York can wait. For now, there are folk to be entertained in Newton Stewart and he must go and get ready for them. "I just love rolling along on two wheels," he grins, still more at ease with pedalling than peddling the Danny MacAskill brand.