It's not a criticism, per se. All of us are getting older, and thereby experiencing receding hairlines, expanding waistlines and deepening facial lines. Unlike the rest of us, however, the rebel yeller's formerly youthful features have been preserved in MTV video amber, and when occasionally re-broadcast by a nostalgic VJ, we get reminded, jarringly, that Billy Idol is no punk spring chicken. By his own admission, he's partied a lot, and it shows.

Billy Idol is, however, genuinely funny and friendly, with a firm handshake and a desire to be helpful. He's almost impossible to dislike, however much he (and his famous videos) have been lampooned by satirists as diverse as David Lee Roth or Eminem. Nor does he does take himself particularly seriously, unlike many of his contemporaries.

Born William Michael Albert Broad in Stanmore, Middlesex in 1955, Billy - as he delights in telling you - was kicked out of Boy Scouts for "snogging" with a girl. He was an inattentive student, and was thereby called "idle" by one of his teachers - the very name he would later gleefully adopt. When he was nineteen or so, Billy quit Sussex University and relocated to London, where he hooked up with fellow Sex Pistols fans Siouxsie Sioux, Steve Severin, Sue Catwoman and Clash guitarist-to-be Mick Jones. The gang, which favoured shocking clothes and behaviour, dubbed themselves the Bromley Contingent, named after the South London suburb where a few of them had lived.

In 1976, the year the Ramones' first album set Britain ablaze, Billy joined the punk group Chelsea. Idol played guitar, Gene October sang, and future Sisters of Mercy bassist Tony James played bass. Idol and James soon left to form Generation X. Right away, the band, with their unabashed pop sensibility and unapologetic image-consciousness, were noticed. Record Mirror called them "one of the most entertaining and vibrant bands to spring from the initial British new wave explosion." In the New Musical Express, Tony Parsons, tongue firmly in cheek, called them "clean punks" who were therefore "[a] menace to our kids." Idol, Parsons wrote in January 1977, "while coming out with the standard lines putting down age, stagnation and the establishment, looks pretty enough for girls whose big sisters used to swoon over Marc Bolan."

And that, pretty much, was Billy Idol's punk rock dilemma. He and James could write terrific punk tunes like 'Your Generation' or 'Kleenex', as they did on Generation X's eponymous first LP. They knew the punk scene well, having been part of it from the outset (in James's case, with Mick Jones in London S.S.). But they were, unarguably, too pretty. Unlike Joe Strummer or Johnny Rotten, Billy Idol and his bandmates all had excellent dental work. Unlike Sid Vicious or any member of The Damned you care to name, Idol and Co. had unblemished skin. Hell, in one NME interview, they unwisely (and untruthfully) declared that they did not drink or take drugs. "The revolution can't happen if you're knackered tomorrow," Idol declared.

In the early 1980s, after Generation X's break-up and his move to New York to pursue a solo career, Billy Idol set about consuming drink and drugs with the zeal of a convert making up for lost time. While racking up numerous hits with the execrable 'Mony Mony', 'White Wedding', 'Hot In The City', 'Eyes Without A Face', 'Flesh for Fantasy', 'Cradle of Love', and so on, Idol bought a motorcycle, moved to Los Angeles, and devoted himself to drug addiction. In 1994, he nearly killed himself via overdose.

Apart from bit roles in films like Adam Sandler's The Wedding Singer, no one heard much from Billy Idol for most of the last decade. It was time to sit back and do a bit of evaluation, Idol says, particularly in light of becoming a father. He laid low.

In the new millennium, Idol put out a greatest hits collection, and starting gigging again with his post-Generation X songwriting partner, Steve Stevens. In 2005, the pair put out another record, Devil's Playground, their first in more than a decade. It doesn't sound very punk, but Idol doesn't give a s**t about satisfying the purists, and never did. He gives one of his trademark sneers.

"In punk, you had artists who were maybe painters who'd make music," he says. "There would be people who were artists, who were journalists. You had people turning things on their heads. I mean, someone like me, who wasn't the greatest guitar player in rock, or the greatest singer, could end up writing songs and singing. Punk meant you weren't non-musical just because someone said you were non-musical. There was a need to give people a chance to do different types of things."

In Idol's view, that willingness to be different applies to punk, too. Unlike many punks, current or former, Idol is not offended by pop-punks like Blink 182 or Good Charlotte. Punk could hardly challenge rock & roll's orthodoxies, he suggests, and then turn around and promote its own. That's hypocrisy.

"[Some punks] lost sight about what it was all about," he says. "It's not just about music, it's not just about fashion. It's not just about three minute songs... It's about passion. It's about being alive, about what you really think is right, what you want to do, and not being f**ked over by some little sod with the right shoes, you know?" Fair enough (and he is wearing big black boots, in case you are wondering). But did Billy Idol have to, well, become such a bloody pop star? I mean, was it absolutely necessary that he go and do something awful like that?

"Look," he says, "if you have a hard time growing up or whatever, you know, you can sing about that. It's your choice. But I think it was Johnny Rotten who said that we don't want all the punk bands to be the same. Fine. So why should every punk band have to be political? That's my point.

"That's what Rotten asked for, really, isn't it? John asked for all of us to be ourselves and to do the music that matters to ourselves. So I did that. I did music that was much more true to me."

Billy Idol's music may be hard to listen to now, but it's hard to argue with him. Looking older than he used to but sounding wiser than he perhaps once was, Idol shakes my hand and walks out to the next interview.