Public Enemy were the Sex Pistols of rap - but they're still seeking the respect they deserve. Johnny Davis talks fighting the power and milking cows on TV with Flavor Flav and Chuck D.

On Public Enemy's 54th world tour, it's Flavor Flav who brings the noise. 'Bitch!' he screams. Moments before the rappers are due to perform, he has arrived backstage to a terrible discovery. He's forgotten his clothes. 'Where did I put my red hat and glasses? I put them in the other fucking bag like a fucking numbskull. Have I got time to go back to the hotel?'

He has not. Tonight Flav will have to perform in civilian gear, though it's doubtful anyone will notice. He's wearing a powder blue tracksuit - accessorised with groin-length gold chains - eight sovereign rings, stripey baseball cap and joke-shop sunglasses. (He has remembered his trademark clock. Worn around the neck, the torso-sized prop is set to 6.05, so he 'always knows what time it is'.)

Live, Public Enemy - Flav, Chuck D, Professor Griff and rookie DJ Lord - belt out classic after classic. 'Don't Believe the Hype'. 'Welcome to the Terrordome'. 'Fight the Power'. They sound terrific. In a show that nudges three hours, they encourage the audience to do the black power salute, admonish the wrongdoing their brothers suffered over Hurricane Katrina ('Fuck George Bush!' everyone chants. 'Fuck Tony Blair!') and hold a competition to find the room's best MC.

Afterwards, while Chuck tucks into his vegetarian supper backstage, Flav continues to rally the audience. For a further 15 minutes he remains on stage, praising God, warning of the perils of smoking crack and thanking everyone for their continued support. 'If it wasn't for you,' he says, 'this show wouldn't be happening.'

Tonight Public Enemy are playing a bar above a Pizza Hut in Stockholm. To 250 people. Not one of whom is black.

Public Enemy's appeal, it's fair to say, has become more selective.

Last year, they put out a greatest hits collection. In the UK, It reached number 38. Recent albums haven't done that well. Some only appeared on the internet. One was recorded in a shed at the bottom of Chuck D's garden.

Meanwhile, Flav has thrown his lot in with reality TV. British viewers have watched the one-time touchstone for militant politics and racial anger mucking out stables with Keith Harris and Orville on The Farm . In America, Strange Love - a spin-off of VH1's The Surreal Life , in which he had a relationship with Brigitte Nielsen - was deemed so interminable, even Chuck D wrote to the TV company to complain.

Plenty of big bands get small. But Public Enemy were pioneers the Sex Pistols or the Beatles of rap. With a run of remarkable albums in the late Eighties and early Nineties, the New Yorkers redefined not just what a rap group could be, but the role musicians could play in culture. 'We don't appreciate being written out of history,' says Chuck. 'We keep hearing about the Who, about Cream. I understand they made a contribution, but shit.'

'Rap has become a sad reality,' says Griff. '50 Cent comes out with a movie that's a step-by-step instruction in how to be a thug. And sells it to children?'

When Chuck D made his first record in 1987, aged 26, many considered him too old to do so. Yet his age defined Public Enemy. Chuck's formative years were framed by the Black Panther Party, the Nation of Islam and Vietnam. He remembers being in third grade when Malcolm X was assassinated. His mother went to work dressed head- to-toe in black, commenting that her white colleagues were petrified they'd never seen so many black people moved by one man. Pro-black: it was how young Chuck was encouraged to think.

Public Enemy came together at Long Island's Adelphi University. Chuck, born Carlton Ridenhour, studied graphic design, his cartoons featuring on flyers for Spectrum City, local parties run by DJ Hank Boxley ('Shocklee'). The pair teamed up with Bill Stephney, host of one of New York's first rap shows, on station WBAU. Shocklee mixed records live, while Chuckie D - his new radio name - talked over the top in a severe baritone copied from basketball commentator Marv Albert.

Others dropped by WBUA, including Richard Griffin (Professor Griff), director of a martial arts school and a Nation Of Islam devotee, who would handle Spectrum City's security with his Unity Force team. Also on the scene was William Drayton, nicknamed Flavor Flav after his graffiti tag, and given a show alongside DJ Mellow D (Norman Rodgers, soon to be rebranded by Chuck as Terminator X, a name he disliked): it featured recorded announcements from train stations, sketch songs and skits on Flav's idiosyncratic look: leather deerstalker, swimming goggles and up to five jackets, worn simultaneously.

Chuck graduated and landed Flav a job delivering furniture in his father's U-Haul truck. Meanwhile, local producer Rick Rubin tried to sign Chuck to his new Def Jam label. Initially, he resisted - 'I was already a certain age. I looked at being an entertainer as a step down' - but was soon recording with a quartet that included Shocklee and Stephney. As the Bomb Squad, they would become one of music's most exhilarating production teams. Lots of groups aim to make ageless music: Public Enemy succeeded. Because the Bomb Squad appropriated sounds that had nothing to do with the contemporary scene, those first albums sound as thrillingly new today as they did 20 years ago.

Chuck road-tested tracks on his girlfriend. Anything she liked was scrapped: it was deemed too soft. 'Musicians said we're not making music, we making noise,' remembers Shocklee. 'I wanted to be music's worst nightmare.'

One afternoon sometime earlier, Chuck D and Professor Griff are being driven through London. They are promoting Public Enemy's most recent release, the property of Chuck's online record label Slam Jamz. Like many of their albums, it has a tortuous pun for a title: New Whirl Odor . 'The world is a ball of confusion,' explains Chuck, who is given to speaking in rehearsed soundbites. 'The album is a global warning against the weapons of mass distraction. They could be anything: a video game, a religion. What are they distracting you from? Thinking.'

Having spent the morning at MTV and scoring free trainers from Adidas, Chuck and Griff are on their way to E4, to record a show in which they'll choose their favourite videos. To help them, E4 has provided a catalogue of the available videos. They're at a loss to find much they like.

'Yo, Chuck, Antony And the Johnsons?' snorts Griff. 'Bring that beat back.'

'Bring that meat back,' giggles Chuck.

They don't much care for music television. 'Giving your video to a sea of paper like that?' says Chuck, shaking E4's list. 'Intermediaries are judging your art before it even gets to the public. That's why the internet is a beautiful thing. Unlike MTV, it's not based on exclusivity of power.'

On the show, Rick Edwards, the presenter, asks what music Public Enemy rate. They say Run DMC. Anyone more contemporary, Rick wonders. After some thought, they plump for Talib Kweli and Common. 'They're certainly hip,' struggles Rick, whose audience is teenagers, 'but what about the more mainstream... 50 Cent?' This elicits a weary sigh from Chuck. 'There has to be a way of judging on quality of music, not quantity,' he says.

Then Rick asks about Flavor Flav and The Farm . 'That dude was over here milking cows,' says Griff. 'One day you're in Public Enemy, the next you're milking cows? How do you justify that?'

Off air, Griff addresses E4's production team. 'I actually heard it was a bull. He was trying to milk a bull with two hands. "Wait a minute... this isn't a cow!"' Griff is giggling so much he has to stand in the corner of the studio, hunched over in hysteria.

'

When Public Enemy signed to Def Jam in 1986, Rick Rubin couldn't understand what Chuck saw in Flav's clowning. Yet aside from being a comic foil to Chuck's imperious lyrics, he's their most musical member, proficient in everything from drums to oboe. 'He can play 15 instruments,' says Chuck. 'I can't play lotto.'

Griff also expanded the group's parameters, calling himself Minister of Information, the title Eldridge Cleaver held in the Black Panthers. He used Unity Force as on-stage bouncers, renaming them Security of the First World, or S1Ws. Looking, sounding and acting like nothing before, Public Enemy recorded their first album, Yo! Bum Rush the Show . Their goal was to make the cover of Rolling Stone . 'Make every track political,' said Stephney. 'Statements, manifestos, the whole nine.'

Before it was even released, the group opened for Def Jam's Beastie Boys in 15 cities at the height of License To Ill madness. If their abrasive, siren-driven racket proved tough for the Beasties' fratboy fans to fathom, that was nothing compared to their stage show: quickstepping S1Ws in military fatigues brandishing plastic Uzis, offset by the bendy-limbed Flav spouting slang: 'Yeah, boyeee!'

Chuck's iron hand ruled. 'You won't see Public Enemy with no 40s and no blunts putting anything in our bodies that'll be detrimental to our existence,' he said, years before Flav would have problems with drugs. Celebrities who wished to go backstage to meet Public Enemy after attending a show were barred from doing so. Perhaps unsurprisingly, Yo! Bum Rush the Show was initially Def Jam's worst-selling record.

Then Chuck hit on an idea to conquer a territory no other US rap group cared about - the rest of the world. Touring Europe with LL Cool J proved instructive: while audiences chucked coins when he crooned his hit single 'I Need Love', they raved over Public Enemy. 'London wasn't into soft music,' Chuck recalls in his book Fight the Power. 'They wanted their music rock-hard. Our attitude was like Mr T and Rocky downstairs in the basement listening to a radio with a hanger sticking out of it doing push-ups. LL was staying in suites in the hotel. [For us] it was like being in the service.'

In September 2005, Public Enemy received a Mobo Award for Outstanding Contribution to Black Music. After a montage of their early videos, an older and wider Chuck took the stage in London's Albert Hall and gave a long, coherent speech: 'I've very proud of you, UK. You're way more talented than anywhere else in the world.'

Afterwards, Chuck waited for a car to take him to his hotel. A few feet away Lemar and Rita Marley - Bob's mother - were signing autographs, but nobody bothered Chuck. 'Public Enemy is like the Rolling Stones,' he says. 'You dip your toe back in and - boom! - it's Steel Wheels .'

It is Public Enemy's back catalogue that keeps them afloat. But unlike, say, Duran Duran or the Pixies, they've never really been away, so there's no opportunity to key into the nostalgia circuit. The failure of their Greatest Hits was a case in point.

'When people say "You didn't make the charts", we first of all have to weigh those charts,' says Chuck. 'What do they represent? Sales? Well, I'm sure dog food outsells all the records in the charts.'

Today, Chuck and Griff are increasingly drawn to lecturing in schools and writing books. 'Books stick around longer than records,' says Chuck. 'Not everybody can write a book.'

In his book Fight the Power , Chuck rails against everything from Hollywood to the sports industry for portraying blacks as 'watermelon stealin', chicken eatin', knee knockin', eye poppin' lazy, crazy, dancin', submissive, Toms. Coons. Mulattoes, Mammies and Bucks'. Griff is writing an expose on 'global white supremacy and all of its attributes'. It sounds exhausting being in Public Enemy. What still drives them? Anger?

'Making a living,' says Chuck. 'That's what drives me. I still don't see how Jay-Z and Puffy are worth what they're worth. I must be doing something wrong.'

Public Enemy were at the height of their powers between 1987 and 1992. More than anyone, they were responsible for taking rap global. They played everywhere, yet never alienated their core fans. In six months alone they toured with Sisters of Mercy, Gang of Four and Anthrax. On U2's Zoo TV tour, they performed to hundreds of thousands.

1988's It Takes a Nation of Millions to Hold us Back was rap's high-water mark, ushering in a new wave of black nationalism despite lyrics that seemed to belittle women and gays. Controversy surrounded 'Don't Believe the Hype', a song name-checking Nation of Islam leader Louis Farrakhan, whose views Chuck was forced to defend. 'Mr Farrakhan is speaking from a Muslim point of view,' he explained. 'He's not anti-Christian, anti-Semitic or anti-anything.'

'Fight the Power', written for cultural soulmate Spike Lee's urban morality movie Do the Right Thing , included Chuck's line condemning Elvis as racist, plus Flav's searing response: 'mother-fuck him and John Wayne.' It was fighting talk music as politics like never before.

Less welcome was Professor Griff's 1989 interview with the Washington Times where he condemned Jews as responsible for 'the majority of the wickedness that goes on across the globe'. Chuck dealt with the uproar by firing Griff, reinstating him, firing him again then disbanding the group, announcing that Public Enemy were 'boycotting the music industry'. They were back for 1990's Fear of a Black Planet which featured a witless Aids skit 'Meet the G Who Killed Me' and 'By the Time I Get to Arizona' which berated the state's refusal to dedicate a holiday to Martin Luther King. (One was established in 1992 in common with the rest of America's states.)

Fear ... marked the end of Public Enemy's glory years. Dodgy decisions (1992's B-sides compendium, Greatest Misses ) and the explosion of MTV-friendly rap conspired against them their popularity waned. Stephney and Shocklee fell out. Terminator X bought an ostrich farm in South Carolina.

In 1993, Flav discovered 911 wasn't a joke when he was charged with attempted murder and imprisoned for 90 days for shooting at his neighbour. Domestic violence, cocaine and marijuana charges followed. Then he checked into the Betty Ford Centre for crack addiction, before breaking both arms in a motorcycle crash. In 2002 he spent nine weeks in Rikers Island prison for driving with a suspended license, amassing an ocean of parking tickets and showing up late for his probation officer.

With this hullabaloo, you have to wonder if Chuck hasn't felt rather let down by his bandmates over the years. Having established Public Enemy as ruthlessly puritanical, it's hardly on-message to cultivate a crack habit. (Chuck is teetotal. He's never drunk coffee.) 'There's plenty of regrets,' he says. 'There's tons of mistakes. But that's life, man. What we can do is go forwards.'

One thing that still rankles is Flav's decision to make some fast cash via reality TV. 'Chuck and Griff thought their boy Flav was a little nutty,' agrees Flav. 'I snuck surprises on them. I should really have talked to my group. But at the end of the day, it's me who lays down with my stuff, not Chuck and Griff.

'You know, Public Enemy has never been against animals. It has always been against racism. When I rocked The Farm that was one of the greatest experiences of my life. Washing sheep, milking cows. We had to help the pigs have sex, so they could have more pigs.'

Flav has recently moved to LA, to try to make more of a career in television. 'I'm just trying to stay on TV, man. After me and Brigitte [Nielsen] broke up, my new show is about me finding new love. It's called The Flavor Of Love . You heard of The Bachelor ? This is The Blackchelor.'

Being famous, he says, suits him. 'I'm a real big celebrity. I'm this megastar. When I was in jail, I was a lot of people's favourite person. I practically ran the jail. I had more freedom than the police.'

He's got rather less freedom now: 48 traffic convictions earned him a permanent driving ban.

'To tell you the truth, that's inaccurate,' he says. 'I had 78.'

Earlier that evening, Public Enemy played a show in London. Tickets had not sold well, and half the venue was closed off. On stage, Chuck gave his speech about the weapons of mass distraction and praised 'all my brothers and sisters from the Caribbean', though it's hard to see who in the audience he was referring to.

Then the show ground to a halt. Someone started chucking cans of Red Stripe at them. One hit one of the S1Ws, exploding down his front. Griff came to the front of the stage, furious.

'We're up here trying to educate people,' he fumed. 'And you throw cans at us?'