Will the real Michael McIntyre please stand up?

From out of nowhere, he became Britain's biggest comedy star. But who is Michael McIntyre? And what exactly does he want?

Michael McIntyre never stops beaming, never stops punctuating his commentary with hearty laughter, not even when he is recounting how, not so very long ago, he broke down in public and sobbed at the failure of his career to take off.

He tells me how he wept as he sat in an Edinburgh café with his wife Kitty, after yet another year of going unnoticed at Britain's premier comedy festival. "I thought I was being completely overlooked," he says with an unnerving guffaw. "It was hell on earth and I cried in Starbucks on the Royal Mile. It's really tough at Edinburgh, it's really tough. I think it's the last time I actually cried."

Being McIntyre, however, he turns the story into an amusing anecdote. "My wife said, 'It's not that bad, there's always somebody worse off.' And I was like, 'What do you mean? Who?' And she pointed out the window and there was some bloke with a toilet on his head. He was flyering his show. I thought: 'Pull yourself together, Michael, you're not advertising the fact that you have your head in a toilet.' "

This sob story is all the more remarkable for the fact that it occurred as recently as 2004, since when McIntyre has gone on to become the biggest star in British comedy with his own Saturday-night show on BBC One and the most successful debut DVD ever for a stand-up, Michael McIntyre Live & Laughing. He is currently in the middle of a 59-date arena tour that includes five shows at the 18,000-capacity O2 and six more at Wembley. And they are selling out.

So he can laugh at his previous misfortunes as he sits in a plush 20th-floor hotel suite looking out over the rooftops of Mayfair and the autumnal foliage in Hyde Park. "I was dismissed all the time, but I'm over it now because everything has gone my way and I'm really happy."

Yet extraordinary as it now seems – given that McIntyre's new DVD Hello Wembley! will be the entertainment of choice in thousands of British living rooms after this year's Christmas lunch – those tears in Starbucks were followed by further humiliation. Back in London, scratching out an existence on the club comedy circuit, he was forced to accept a gig as the reserve funnyman, known in the business as "the spare", hired in case someone on the bill doesn't show up.

McIntyre, already by then an experienced stand-up with six years of hard slog behind him, recalls the brief as "one of the most depressing moments of my life". Then the headline act at the club, Jongleurs in north London, failed to appear. "And they wouldn't put me on, they wouldn't trust that I could close the show in Camden. That makes me so angry," he says, laughing once again but almost in disbelief at the recollection. "So I'm sitting there and they didn't trust me to do my job, in Jongleurs, which is not exactly the pinnacle of the circuit, in fact it's the lowest ebb of it.

"I was on the phone to them and they said, 'Well, you've never headlined for us before.' I mean, Jesus! It really annoyed me ... and that wasn't so long ago. They didn't rate me at all. At all. And I wasn't that much different – in fact, a lot of the jokes that I had then have gone on to be massive jokes for me."

McIntyre doesn't need that booker now that – at the age of 33 – he's performing on stages so big he requires giant screens to project his image to the fans in the back rows. He bounds on to the stage at the O2, his arms swinging at his side in what has become his trademark skip, and he says: "Because this is the biggest gig of my life, quite a lot of people have shit seats. I'm sorry!" Of course, he's not really upset that the punters in the Gods have "Sat-navs that say I'm still a mile from the venue" because this is what he's always wanted. "I love being on stage more than anything else in the world," he tells them.

It didn't seem quite like that on the opening night of the tour in Cardiff, his first experience of stand-up in an arena venue. "I was completely shocked and after 15 minutes I was hyperventilating. I was in serious trouble," he says, chortling at the memory. Attempts to disguise his problems were doomed by his use of a Madonna-style headset microphone that relayed the sound of his heavy breathing. "I was seriously panting."

No matter, because "they were so on my side, the audience". Just as they were later in the tour when he inadvertently belched into the wraparound microphone, and when he performed the opening half of a show with his flies undone. And McIntyre knows he has the audience on board because his success has come through word-of-mouth and the passing round of his DVD among relatives and work colleagues, rather than via the ratings of the critics or the kudos that comes with the Perrier comedy awards.

He stands on the vast stage of the O2, reeling off observational material about his life as a middle-class father of two. "I can't see the audience," he tells me. "I can just hear them, it's a thunderous sound, the lights are in my eyes and I can't see a single person because they've got these amazing low spotlights in your face. I can hear myself really well and I'm completely in my own bubble. And I just get encouragement, I can hear laughs and I'm encouraged to keep going."

McIntyre jokes in his act about having sons called Lucas and Oscar ("You can't get any more middle class than that"), saying that when he called out to Oscar in the park "three dogs came over". He makes no pretence at machismo, expressing his horror at the behaviour in men's changing rooms at gyms ("I've never towel-dried my arse in my life"), and cavorts around the stage demonstrating different styles of Hoovering (walking up and down, or standing in the middle of the room) or the absurd routines we all go through in trying on a pair of shoes, pressing our toes with our thumbs and so forth. Though his Hungarian-born mother gives him eastern European roots he thinks he looks oriental ("a camp Chinese bloke in a pink shirt ... it could be Gok Wan," he tells his audience).

Again and again, it brings the house down, this observation of shared experiences, though it's not for everyone. Vic Reeves recently complained in these very pages that such humour was "about the easiest form of comedy. It's just a warm pat on the back for everyone, saying, 'I've noticed that as well, can we be friends?' "

And while McIntyre's friend the comic Paul Tonkinson congratulated him years ago, saying "you're the middle-class Peter Kay", he says such support is unusual. "A lot of comics who have been doing it a long time have very much the opposite reaction to me," he relates. Why does he think that is? "It's tough isn't it, when somebody comes along and starts doing well? Some people can't cope with that. And maybe if I'm honest, if it was the other way round, I couldn't either; it would piss me off, too."

McIntyre agrees that the sense of him being an overnight sensation plays its part in this resentment. Except that it's not true to say that he hasn't paid his dues. Although his father, Ray Cameron, co-wrote Kenny Everett's television comedy show, which attracted an audience of 20 million in the Eighties, the young McIntyre had no real comedy heroes.

His parents divorced when he was seven and his father, who had moved to Los Angeles, died when he was 17. After attending the "unbelievably upper class" Arnold House prep school in St John's Wood, young Michael was sent to Merchant Taylors' public school in Middlesex, but was obliged to finish his schooling at a state sixth-form college, where he was a loner. "I was a real misfit," he recalls. "I wasn't getting many laughs there. I used to just hide in the library on my own. I wouldn't go to lessons and this was reflected in my results.

"There was a load of cliques: the Jewish girls, the Asians, the rockers. The Asians auditioned me. We were walking past Pizza Express, and I said, 'Ooh, shall we go in here?' and they were, 'No, we're having a kebab innit?' So they auditioned me and then quite politely refused to induct me into their clique. I formed my own clique of one in the library."

He managed to get into Edinburgh University but dropped out after a year. He desperately "wanted to be cool" but couldn't get a girlfriend. "I had a horrific track record at this, as bad as you can imagine. I had really hot girls as my friends but they were not interested me in any other way. Oh my God, it would be literally like: 'You're the funniest guy I've ever met, now I'm going to fuck Frank, can we meet for breakfast?' "

As he tried to crack the Edinburgh Festival, his mother feared he'd starve. His wife, Kitty, an aromatherapist whom he met when he was 23, was also worried. "She doesn't like being reminded of this – but she told me not to do it," he recalls, laughing once more. "She said, 'Are you sure Michael? It's a very difficult thing.' "

He never resorted to introducing gimmicks into his act, however, in order to get noticed. "I always thought 'act' was a strange word – because this isn't my act, this is me. I became a comedian not because I could find a persona as a delivery system, or because I'm a great writer of comedy; my whole show is just a collection of moments that I thought were funny," he says.

Though he went undiscovered by the critics ("They care about finding new talent but they didn't find me"), his fortunes improved as the public warmed to his candour and spread the word. "Luckily it's the audience who have made me," he says. "I'm very honest with them. I'm very open, though it took me years to be as open as I am because I wanted to be cool. Now I just take the piss."

The willingness to be candid was later accompanied by a renewed determination to succeed that stemmed, he says, from becoming a father for the first time, soon after that humbling night at Jongleurs. "It just freaked me out. I looked at his little head which he couldn't even hold up and I thought: 'Oh God, this is serious and I work two nights a week in Jongleurs and I'm on first. I've got to sort my shit out.' "

He finally broke through with an appearance at the Royal Variety Performance in 2006 – and three years on, things could hardly be going better. His BBC One series Michael McIntyre's Comedy Roadshow will be back in the summer and television execs are pestering him to enter the world of game shows and become "Mr Saturday Night". Though he prefers to stick to stand-up – conscious that when he doesn't look like "Pierce Brosnan after a mouthful of sweets", he resembles "Leslie Crowther after a good Christmas" – he has obvious family appeal at a moment when broadcasters are fearful of crossing boundaries of taste.

In reality, some of McIntyre's material can shock. "I don't go out not to offend people, I've got a joke about Michael Jackson," he points out, referring to a gag that reflects on the irony of Jacko's death just at the time when swine flu has brought masks and gloves into fashion. He's had to cushion its impact by inserting the warning "I've got this joke that doesn't work any more" before he tells it.

His Glasgow audience was treated to an anecdote about a Scottish waiter's response to his request for a full English breakfast: "I do this impression of his face contorting like this," he relates, "and I say, 'It was the face of a thousand words, and most of them were ...' " Even now, in a hotel room with no one else present, he refrains from uttering the actual expletive he used in Scotland, observing that "the C word is the worst word that you can use, but it's in character".

Conscious of his clean reputation, McIntyre followed that joke by saying to the audience, in a Scots accent: "We don't need you for that Mr McIntyre, we've got [Scottish comedian] Frankie [Boyle] for that, you stick to your Hoovering jokes."

Comedy, says McIntyre, needs to be a broad church. "Even I will admit that if everybody was like me it would be pretty boring. You need me and you need Jimmy [Carr] and you need Frankie. You can't put me up on a pedestal and go: 'Aaah, this is what we want'. No, this is what you want. Other people want Frankie and he's hilarious."

But many people do want Michael McIntyre. Asked if he laughed at Boyle's controversial joke about the face of Olympic swimmer Rebecca Adlington, he discreetly replies, "I like Rebecca Adlington, she came to my show." Of course. Kate Moss passes round his DVD. Nick Faldo wants tickets. David Seaman is sat in front of me at the O2.

The breadth of McIntyre's appeal is astonishing. From the old lady at the bus stop who tells him "every Saturday night I'm with you, Michael" to the six-year-old in the park who blurts out: "Ooh, Michael McIntyre, I love the road show!" So although he introduces the odd F-word into his show for emphasis, he has removed the saltiest material from his DVD. "I have to respect those people even though it's a 15 certificate. I get people saying, 'I don't get to do much with my son and we sat and had a real laugh together.' "

And that, when all's said and done, is why McIntyre is always beaming too. "I've got a smile on my face because I find it funny," he says. "That's all that I'm doing, I'm just saying things that I find funny."

Michael McIntyre's new DVD 'Hello Wembley!' (Universal Pictures) is out now