Once upon a time, stand-up comedian Dave Gorman went to a London pub to celebrate his flatmate Danny Wallace's birthday and happened to mention that he had heard the assistant manager of East Fife football club was also called Dave Gorman. Ever the sceptic, Danny didn't believe him, so instead of agreeing to disagree, they bought two train tickets to Scotland first thing the next morning and sought out the East Fife gaffer's right hand man. His name was indeed Dave Gorman and so, it transpired, was his son's. Deciding it would be churlish to travel all that way and not meet Gorman the younger, our intrepid duo went and introduced themselves to a very bemused Scottish policeman. Upon arriving back in London, Danny went back about his day-to-day business producing funny radio shows for the BBC, while Dave got out the phone book and began diligently calling everyone listed as "Gorman D." to enquire if their name was Dave.

It was not the first time he had embarked on such a pointless exercise in frivolity. Or the second. Two years previously, finding himself bored with performing the same old same old on the Edinburgh Fringe, he decided to scrutinise the lyrics of Ian Dury's hit 'Reasons To Be Cheerful' and prove that the Blockhead-in-chief's reasons weren't particularly valid grounds for merriment at all. Dave had a vague idea that he would devote approximately 60 seconds to each reason, thus guaranteeing himself an hour long show. However, he quickly realised that the stories behind his attempts to decipher Dury's lyrics were funnier than the actual jokes, and subsequently chronicled his trials and tribulations in a critically lauded performance called, unsurprisingly, Reasons To Be Cheerful. Sadly, illness prevented Dury from attending the show, but his daughter Jemima saw it one night in Brighton, loved it and assured Gorman that her dad had heard all about it and thought it was a fantastic idea.

The following year, Dave found himself bereft of ideas for his fringe follow-up. In an attempt to get the creative juices flowing, he assembled some friends in his local pub and embarked on a tequila-fuelled brainstorming session. The following morning, he woke up in his front garden with no recollection of the previous night's carousing, a new tattoo and nipple-ring, and a beer mat in his pocket with "Do a show about making the world a better place," scrawled on it. Never one to shirk a challenge, he wrote to every newspaper in Britain anonymously, asking people to send him their world-improving ideas. The ensuing deluge of utopian dreams (ranging from the eminently sensible to the pigstick nutty) and his attempts to fulfill them formed the cornerstone of Dave Gorman's Better World, which was acclaimed by several critics as the most innovative comedy show they had ever seen performed at the Edinburgh festival.

Despite these critical bouquets, Dave was forced to wait another 12 months before being nominated for stand-up comedy's bottle-shaped grail, the Perrier Award. His shortlisted show was Are You Dave Gorman?, an intriguing and highly amusing multi-media account of six months spent travelling the world pressing the flesh of as many Dave Gormans as he could find. His quest is currently being broadcast on BBC2 and features a supporting cast comprised of his camera-wielding mate Danny and more Dave Gormans than you can shake a stick at.

With his intense stare, trademark goatee beard and extravagant mutton-chop sideburns, the Dave Gorman other Dave Gormans call That Weirdo Who Won't Leave Us Alone is - there's no way around it - a scary looking fucker. As a bloke, however, he's softly spoken, intelligent, articulate, friendly and very, very funny. I first saw him on The Stand-Up Show a couple of years ago, performing an astonishingly clever routine about maths. It wasn't about his maths teacher's funny mannerisms and BO or the pointlessness of algebra... oh no. It was actually about maths: different types of numbers and their relationships with each other... the sort of seam most physicists wouldn't even consider mining for laughs. And while the actual material was far too complex to remember, it is a routine I will never forget.

And so to today: our first meeting in the flesh over coffees and a tape recorder in a Soho pub and there isn't a facial hair between us as his lush lavish whiskers have been sacrificed for a movie role.

"I'm an itinerant ragamuffin," he laughs. "I'm just a chancer of the highest order. I take work on occasion to pay my way and the rest of the time I have fun. Somebody in The Times wrote that I was loaded from my Mrs. Merton days and that's just not true. Basically, the whole Dave Gorman thing was done on my credit card and I just didn't pay the bill for a while. To be honest, I don't really talk about the money in the show, because spending all that money on a seemingly pointless exercise is not something to be proud of. I have an attitude that I'll always have a job if I want one. If this had all gone tits up I'd have got a writing job, or a producing job, or a script editing job to pay off the debt. It's no big deal because I'm not driven by money."

"With this and with my other shows, I've never pretended that they're ideas nobody else would have," he explains. "The difference is that they are ideas that nobody else would follow through. Some people might think of finding everyone in the world with the same name as them, announce that it's a great idea and do nothing about it. Others might have gone to Scotland to meet the assistant manager of East Fife and then left it at that. There's a line where everybody else would have just stopped, but I didn't. And why not? I have a great time. The way I see it is that I make documentaries out of my life for a living, so I have a duty to myself and the people who pay to come and see my shows to have an interesting life. If I don't, then I've got nothing to say on stage."

As well as Great Britain and Ireland, the Dave Gorman radar has come up trumps in unlikely hotspots as diverse as Oslo, where he woke up without any shoes (it's not in the show because he can't prove it, but he suspects he sold them for drink); America, where he got caught in a tornado while being driven around in a car by a Dave Gorman; and the South of France, where he called to the door of a Canadian David Gorman, only to discover his prey was in London at the time. Along the way, he has attracted an ever-expanding legion of devotees who have left no stone unturned in their quest to unearth more and more Dave Gormans. Indeed, five exceptionally sporting non-Dave Gormans clambered aboard the bandwagon by legally changing their name to Dave Gorman by deed poll.

"Two of them are girls, one of whom is going out with a bloke who also changed his name to Dave Gorman," Dave announces proudly. "Legally, they are both called Dave Gorman. I'd love them to get married and take a double-barreled surname: Mr. and Mrs. Dave and Dave Gorman-Gorman. That'd be perfect."

As I stare across the table in slack-jawed astonishment, the original of the species, Dave Gorman, looks me in the eye and beams.

"I know what you're thinking," he says quietly. "It's beautiful, isn't it?"

The Dave Gorman Collection, Sundays, BBC2, 10:45pm. www.davegorman.com