I don't give a damn about Moyles's insults

"I've never been told to tone down anything," he insists. "What do people mean by laddishness? If it's that crude, phwoar! type of behaviour, then there isn't any of that on the show, anyway. The bulk of our listeners are female, we're not laddish."

Then Vaughan says something really surprising. "I've never particularly bought into that laddish thing. I've never bought a lad mag in my life, I've never really taken to them. I see all of that as a kind of camp misogyny, and an awful loathing of women. It's an actress only being able to get publicity by dressing up like a soft-porn star, and I think it just degrades. Actually I loathe it."

But if there's one contemporary presenter who has come to define laddishness - with his street-smart take on traditional end-of-the-pier humour, his parka and his pint of Strongbow - isn't it him? More to the point, doesn't he do the voiceover on the ads for Nuts magazine?

Vaughan grins and laughs. "Yeah, yeah.

But you know there's no hypocrite like a happy hypocrite. I did a year's worth of those voiceovers at a time when it wasn't quite the same mag. It was meant to be more a GQ thing, I think, and then very quickly it was all about suspenders and shark attacks. I'm not doing them any more. I don't buy into that stuff at all, honestly."

I believe him, for what it's worth - there's a charisma to Vaughan's blokeishness which those nasty lad mags don't have - but it's an undeniably odd mistake to make: hating Nuts, yet taking money to sell it.

He is bullish about his telly career, and the end of the lucrative BBC contract which never really produced a hit vehicle. ("Yeah, it was big money," he says, "but not £5 million, which was what everyone reported. No one is on £5 million.") His most recent venture, C4's Space Cadets - a reality show in which contestants were tricked into thinking they'd gone up into space - "fell between two stools", he says, and should have concentrated more on the technical aspects of training, and less on the humiliation of the cadets.

Meanwhile, he claims to have written "a modern classic" in 'Orrible, his widely-panned BBC2 sitcom. "Videos of it sell for more than £100. This was the original chav comedy, we were just a bit ahead of our time!"

Switching from TV to radio gives him more time with his kids, Tabitha, six, and three-year-old Rafferty, which he loves. "The best thing about my job, the best thing, is being able to pick my boy up from school at midday and actually feel as though I'm a part of his life in that way, rather than just being dad at home in the evenings. I think I'd feel really incomplete without that, those afternoons with the kids."

Vaughan was brought up in Barnet, north London, in a solidly middle-class family, and educated at Uppingham School - though his father, an engineer, went bankrupt when Johnny was 16 and "paying school fees was a bit of a struggle after that". Partly because of the bankruptcy, he did not go on to university, but instead came back to London and started work in a video store. "I was enjoying myself," he laughs, "kind of having an extended gap year, earning money and getting wasted. I had that kind of arrogance: well, I'm a good talker, there's nothing I can't do, and unfortunately that's what I ended up doing - nothing."

He also spent 25 months in Brixton prison for attempting to sell cocaine to detectives at a hotel close to the M1. Nowadays, he views that spell as an education in itself - and suddenly, he's not sounding very laddish at all. "One of the greatest joys of my life is reading books. Really. And I'm so pleased prison gave me that. Prison made it easy to read; that's kind of all I did there."

Afterwards, it was almost impossible to get work. Indeed, Vaughan stumbled into TV: a friend was offering free beer in his garden while Channel 4 filmed a title sequence, requiring a crowd of youngsters, for the pop show Rapido. Johnny got chatting to a producer, who liked the cut of his jib and offered him a job presenting the C4 review show, Moviewatch. Big Breakfast followed, and Vaughan the celebrity was born.

Yet he and his wife, Antonia, a dress designer, are rarely seen on the celebrity circuit. They don't do many celeb parties or premieres and don't hang out with other TV stars. "None of that appeals to me," he says. "If I've got time off I've got people I'd really like to see."

What does he think when he looks back at his career now? "I should have looked harder at my own strengths and been a bit more honest with myself about things," he says vaguely. He has tried to squeeze his particular talent, he implies, into too many wrong TV formats. In America, where he made a game show for ABC last year, more attention is paid to matching star with vehicle.

Vaughan is back on TV later this year in a C4 panel show called Best of the Worst, a comic celebration of badness and failure. He and David Mitchell, of Peep Show, are team captains while Alexander Armstrong, the Pimm's man from the TV ads, hosts the show.

So what can he do to get back those breakfasttime listeners for Capital, I ask at the end of the interview. What can he change? "Nothing," he replies instantly, "because it's a cracking show already. I think we get better and better." He's exceptionally good, Vaughan, at talking himself up, reminding us that he was once very hot property indeed. Reclaiming that ground now, however, appears to depend on absorbing yet more flak - and most of all from a certain fat bloke at Radio One.