It would be almost impossible for Graham Norton to be Graham Norton 24 hours a day. If the sheer effort involved in all that braying, hand-flapping, eye-rolling Irish camp didn’t kill him, a member of the public surely would.

So it comes as no surprise that, when I meet him on a winter’s afternoon in a photographers’ studio in Kentish Town, he is all calmness and diffidence.

Even his boyishly round face – squashy nose, beady brown eyes, pouty lips – seems harder and less animated than it appears on the television. The only Graham Norton thing about this Graham Norton is his clothes: he is wearing a schoolboy’s uniform, because The Sunday Telegraph Magazine has asked him to wear one for the Christmas cover.

The shoot over, Norton changes into tight-fit black cords and a tight-fit pale green designer jumper with a large peace sign on the front. We find a sofa in a quiet corner that turns out to be not so quiet when thumping disco music starts up in an adjacent studio. ‘Never mind,’ he says, patting my tape recorder, ‘it’ll sound like we were having a great time when you come to transcribe it.’

With his neatly trimmed sideburns and full head of closely cropped hair (the white patches are because he suffers from vitiligo), with the sheen of foundation that has been applied for our photo shoot, and with his lithe figure (he lost two and half stone a couple of years ago and has kept it off with the help of a personal trainer), Norton looks younger than his 39 years. Clearly he is no stranger to physical vanity, I say, so why on earth did he agree to dress up as schoolboy?

‘I quite liked the idea,’ he says mildly, wrinkling his nose. ‘It’s Christmassy and I think “naughty schoolboy” is what I am about. Where I get bored is when I show up for a shoot and they want me to wear a feather boa. Too obvious a thing for a poof on the telly to do.’ But surely he has done more than anyone in recent years to reinforce that steroetype of gay men? Indeed a section of the gay community is said to resent the way he has followed in the mincing footsteps of Larry Grayson, Kenneth Williams and Frankie Howard, perpetuating the idea that a gay man cannot succeed on television unless he is insanely camp.

‘Yes, well, it’s not a lie, I suppose. I am camp. Lots of gay men can’t cope with thier campness. They are in denial about it. So every gay personal as says “straight acting”.

“How straight acting?” I want to ask them. “Do you sleep with women?” No. I understand it, though, this urge to be seen as straight. Because society places a value on masculinity, gay men aspire to it. If you go to a gay club and the doorman says, “You do realise this is a gay club, don’t you lads?” you get all excited because you think, “Wow, he thought I was straight!”‘

Norton pauses to flick imaginary dust off his knee. ‘That said, I did feel Uncle Tom-ish when the writers who do the opening gags on the show made me play a straight person’s version of a gay man. There’s less of that now. You know, all the anal jokes and innuendo. I went along with it because it got a laugh. I guess I was lazy. I should have made more of a fuss.’

Is it that he is just shallow? ‘Probably. I do get pleasure from very inconsequential things, like shopping for clothes. I think things that are popular are interesting. What appeals to a mass audience, suddenly, overnight, fascinates me. I feel in tune with all that.’

And perhaps this is why Graham Norton is considered the hottest property on British television at the moment, and why he will be on our television screens almost every night over Christmas (Norton turns up again in the new year with a documentary about Shanghai). Not long ago the BBC tried to poach him for £5 million for a two-year contract but he decided to stick with Channel 4 (where he is paid £1 million a year plus bonuses for his five-nights-a-week show, V Graham Norton), because he felt Channel 4 was the natural home for his brand of smutty humour.

Since winning the Best Newcomer prize at the British Comedy Awards in 1997 (after standing in for the Channel 5 talk-show host Jack Docherty, who was expected to win the award and, even more embarrassingly, was sitting at the same table as Norton for the ceremony) Norton has become the face of Channel 4. His viewing figures are high, he has won two Baftas and an Emmy, and he never passes up an opportunity to plumb new depths of bad taste.

To see in the new millennium, for instance, he asked a female guest on his show to fire 12 ping-pong balls from between her legs on the stroke of midnight. In another wheeze he found people with funny names, such as Mrs Djerkoff and Mr Bollacks, and phoned them up.

When Sir Elton John appeared on the show he found himself playing with a vibrator attached to a football and talking on a cuddly-dog telephone to a deranged fetishist in a silver lamé astronaut suit, who reached sexual climax mid-conversation.

Norton’s fans claim that what he does is in the tradition of saucy postcard British humour. His critics say that the jokes about bodily functions might be bearable if only they were packaged with a hint of imagination or humility.

Does he consider himself the apotheosis of vulgarity on television? ‘Usually, if the papers described the awful things we’ve done, I always think, “That sounds great. I’d forgotten how funny that was.” I don’t see the harm in the show. Occasionally we cross a line but we are self-policing. It’s not a discussion programme. It’s childish and innocent. The only test is, is this funny?’

Where does he personally draw the line on, say, pornography? ‘I use it myself but I don’t think you can generalise about pornography because some of it goes to very dark places. When you see a woman performing fellatio on a horse you just think, “I beg you, get a new agent.” But I don’t think the world is getting more evil. I think it’s getting nicer.’

Even so, does he feel no guilt about the part he might have played in dumbing the nation down? ‘I don’t think I’m leading the nation astray. I think the show is reactive. Our show is mainstream. That is where ITV went wrong. They lost touch with what real mainstream is. I think television is playing catch-up with the public. The internet has opened up a strange and interesting world, and I think we are reflecting this rather than introducing viewers to it. If I ever thought our show was harmful, I would be upset.’

The funny thing is, I think he means it. Graham Walker (Norton is a stage name) is a more sensitive and reflective man than you would imagine him to be from seeing the sniggering, self-regarding character he steps into on television. And though he claims to be lazy there is a steeliness and self-reliance about him – perhaps an inevitable consequence of his only having found success after years of failure.

Graham grew up in the market town of Bandon, near Cork. His father, Billy, who worked as a sales rep for Guinness, and his mother, Rhoda, were among the few Protestants living in a mainly Catholic area and sent Graham and his sister Paula (two years his senior) to a Protestant boarding school.

Graham was considered a bright pupil and won a place to read English and French at University College, Cork, only to drop out after a year to live in a hippie commune in San Francisco.

It was run by a bisexual man twice Walker’s age who smoked dope, encouraged his followers to grow their own food and make their own clothes, and subscribed to the principle of free love. After a year Norton returned, went to England and enrolled at the Central School of Speech and Drama. ‘I wanted to be a serious actor but when I tried to be serious it looked like I had stopped. My brooding silence looked like someone had turned me off.’

Unable to find acting jobs he worked as a barman in London and won a reputation for being witheringly rude to customers, who thought him hilarious. In the early 1990s he decided he would try to earn a living from making people laugh, rather than do it for free. His stand-up work led to him being given a cameo in Father Ted and this in turn led to him standing in for Jack Docherty for one fateful week in 1997. As a consequence Channel 4 gave him his own show, So Graham Norton, the next year.

While at university he had what he describes as a ‘psychotic episode’ in which he locked himself away for several weeks and collected dead flies. How did he not give in to depression during the wilderness years that followed university? ‘I did become a little bitter when I was working as a barman. But since I’ve been working in television there really haven’t been days when I feel down. I’m one of those annoyingly happy people who like their work. I only get miserable when I allow myself to get miserable, on a weekend. I’d be deranged to do what I do in front of an audience if I was prone to depression.’

He thinks he could live without television though, if his career ever fizzled out. ‘I certainly wouldn’t ever stoop to going on Celebrity Big Brother. I have no idea why they do it.’ He grins and covers his mouth with his hand. ‘At the same time, you never know. I wouldn’t be that surprised if I ended up in the house. I don’t know how much you miss fame when it’s taken away. Is it like scoring drugs? Driving around the back alleys of television scoring a bright light? Trouble is, if I was on Celebrity Big Brother I couldn’t behave as I do on my show because there are knives in the house and someone would stab me, mid-afternoon, day one.’

Actually someone did once stab Graham Norton in the chest with a Stanley knife while he was walking through Queen’s Park. The gang of muggers left him for dead and he nearly did die from loss of blood while waiting for an ambulance. ‘My great fear was to die alone,’ he says. ‘Someone to hold your hand. When I thought I was about to die and my body was closing down, I did instinctively ask this [passing] old lady to hold my hand. It didn’t matter who it was. A nurse’s hand would have done. It taught me that you do absolutely need to hold on to life, someone living, as you die. And I’m not a very tactile person. It was very out of character for me.’

This glimpse of his own mortality made him worry about growing old alone. He is said to be very generous and loyal to his friends but something of an island when it comes to relationships. He thinks he’s been in love three times. ‘My version of falling in love is borderline psychotic. Should be avoided at all costs. Get obsessed. Can’t fall in love and function at same time. All-consuming. Tunnel vision. Euphoric.’

Shortly after dropping out of university he nearly married an American girl. He even brought her home to Ireland to meet his family. ‘We were engaged,’ he corrects. ‘Which is not quite the same as nearly married.’ He wasn’t feeling sexually confused at the time, he says. ‘It was a sort of reluctance. Friends kept telling me I was gay and I resented that. I wanted it to be my choice. I did have sex with women. And the woman we are talking about, I would still say I was in love with. I’ve lost touch with her now, though. I saw her six years ago with her husband or boyfriend, and it was odd because she talked to me like an ex boyfriend, and I felt so alien in that role because my life had changed so much.’

His longest relationship, with Scott Michaels, an American producer, lasted for five years. They are still friends but they no longer live together. His fame came between them: Scott later said, ‘Graham’s career always came first.’ He isn’t in a relationship at the moment: ‘Relatively available, but not to live with,’ he says.

Is it that he is difficult to live with? ‘Impossible. All of my day is spent dealing with other people. When I come home I like it to be empty. The presence of others in my house kind of annoys me. I love coming home and shutting the doors. I feel brain-dead.

‘If I go out to dinner after a show, I have nothing to say. I just stare at the food. By the end of the day I’m bored with being Graham Norton. At dinner parties I do tend to sit back quietly because I feel sorry for other guests when I arrive and they say, “Oh fucking hell, this is going to be a nightmare. How annoying, him blabbing on all night.” So I clam up to avoid annoying people.’ Does he annoy himself? ‘I can’t watch repeats of my show,’ he says.

Now that he is rich and famous, does he suspect the motives of potential suitors? ‘Yes. I do. And I make a decision about how much I care! Everyone sleeps with someone for some reason. If you have an interesting job or you have money or you are on the telly, people might find that attractive. That’s OK.’

He never felt comfortable with himself, he says, when he was two and a half stone heavier. Changing his physical appearance helped him feel more confident that people were attracted to him for the right reasons, not just for his fame: ‘I feel less humiliated. It’s already wearing off, though. There was a year when I felt slim and fit. Now when I am out I feel 40 and that’s not a good thing. I lost the weight because of television, though. In life when you leave the house and look in the mirror and think, “I look OK,” you can carry on thinking you look OK all day. On television you see your arse going up the stairs. I was constantly being reflected in an unforgiving mirror. If you aspire to be on television you don’t want to be hard to look at.’

Endearingly, he thinks there’s something rather sexless about him. ‘I’m a sexual tourist,’ he says. ‘That’s how I am when I ask the audience questions. Everyone is interested in everyone else’s sex lives. They are not interested in their own. But I think people are more prepared to talk about sex in this country than they were, so long as it is funny. Serious documentaries about sex are just awful. It has to be funny. Sex is funny. It’s God’s joke: to make you feel like that, you have to do this.’

Norton doesn’t go along with the rather easy analysis that his adult obsession with the subject of sex is a consequence of his repressed Irish Protestant upbringing.

‘I think I was obsessed as a child as well, though. Who knows how Ireland affected me? I did always feel foreign there. Not part of the crowd, which I suppose was something to do with me being Protestant in southern Ireland. And being gay, of course. I was camp even as a child.’

Was his father camp? ‘No. But he was a gentle man. He was a hard worker. I always remember when I moved to London and I proudly showed my parents my favourite shirt shop, which I thought was so cool.

I remember them looking at it so blankly and thinking, “Why the fuck is he showing us that?” It did put it into some perspective. I just happen to like the flim-flam of London.’

Although he says he is gentle like his father, Graham Norton does have one outlet for manly aggression: his car, a black jeep. The interview done, he gives me a lift to the Tube station in it. ‘I am bad in the car,’ he says looking over his shoulder as he reverses. ‘I do lots of shouting with the windows up. Tirades of abuse. I really love it.’ Just as I am beginning to wonder if this is an example of him ‘straight acting’, he adds, reassuringly, ‘I’d be terrified if someone could lip-read, though.’