Hard man, hard job

Jason Williams is a man with a secret. For a start, Williams is not his real surname - but the quietly spoken 31-year-old becomes jittery when pressed. Nor will he reveal anything about his private life, beyond owning a house "somewhere in the Midlands", having a partner of seven years, and studying film and media "at a new university" before starting a career in television. He is concerned, a colleague later calls to drum home, that any location more revealing than "the Midlands" could place him in immense personal danger. Jason Williams, you see, is television journalism's invisible man.

Over the past two Sundays, Williams's disturbing 10-monthlong exposé of Britain's hooligan underworld has made compulsive viewing on BBC2. Unlike Donal MacIntyre, whose own foray into the Chelsea Headhunters three years ago sent two men to jail, Williams does not relish a starring role in the year's most gripping documentary. Working with a hidden pinhole-sized camera and a microphone sewn into his Stone Island jacket, he is never actually seen on screen throughout Hooligans, which concludes on Sunday at 9pm. He remains a disembodied voice who befriends the hard men of Millwall and Cardiff and stands by as they kick down rival supporters or set fire to pubs.

"That's not to say I haven't gone through the full range of emotions that Donal experienced, such as when a south London mother runs screaming into the street with her baby to confront rioting Millwall fans," he says. "But maybe I'm just a bit old-school, and think it's better just to show the bare bones."

Since he began infiltrating hooligan "firms" last August, Williams has feared reprisals from those he has exposed. He would always stay within feet of his Special Forcestrained bodyguard, and although he has rejected use of a BBC safe house, he is at pains to retain his anonymity. In part, this is because a previous investigation into Yardie gangs helped convict gang members for firearms offences. Another surveillance project involved international drug smugglers.

Williams knows there are quite a few people out there who would like to find him. "If any of the hooligans knew where I was, I can't imagine they'd be rushing to buy me a pint," he says. "I took the rubbish out yesterday and noticed myself looking over my shoulder."

The series does them no favours. We see Lennie, bad boy of the Wolves Subway Army, in action: "I wanted to do the f - ing Old Bill. I f - ing hate them." At Millwall, we watch from inside the police cordon as fans attack a police horse and set fire to a van. From the back of a private hall, we see Cardiff City's controversial owner Sam Hammam deep in discussion with known hooligans who have links with far-Right groups such as Combat 18. All Williams needs - beyond their trust - is his £2,000 Sony camera kit, comprising a tiny lens linked to a 2in by 1in circuit board inside his jacket lining, with the on-off button hidden in his pocket. "It's just stuff you can get in Dixons nowadays."

Filming undercover, he says, combines excitement with extreme danger - feelings also identified by hooligans who unknowingly shared their own motivation with the camera. "It's exciting because of the complete adrenaline rushes it gives you," he says, "and dangerous because of the fear of exposure." He never forgets that the wrong judgment could imperil his physical safety - or, worse, waste months of filming.

The infiltration process proved rather easier than that practised by MacIntyre, who had himself tattooed in order to fit in. Williams merely went designer shopping. "If you've got a lot of face and you look the part, they accept you," he says.

This meant buying into the uniform: a Burberry or Lacoste shirt, Stone Island jeans, Camper shoes. "That's all you need to be seen as a lad. It's funny, but on their internet chatrooms, the hooligans seem to be praising me for having a lot of bottle. They're saying we've told it like it is, and rather like the programmes."

On the underground In The Know website, where his subjects are debating whether they had suspected his deception, "BoroBhoy" declares in a typical comment that "it was a quality programme, can't wait for next week".

During the past season there were more than 50 serious incidents of fan violence involving English clubs, many of them unreported in the press. Williams's achievement is to document just how well-organised are the gangs, comprising as they do working men (and very occasionally women) mainly in their thirties and forties.

Using intelligence from the police and anti-fascist groups, Williams befriended gangs such as Cardiff City's Soul Crew and the Wolves Subway Army so that he could be there to witness violence first hand. "I'd get as close as I could without showing my hand," he says. "It meant being a lad down the pub with them on match days and showing I knew enough about the scene. But I was also filming, so I had to see myself as a human tripod, tracking people as they came down the street. In the pub, that meant keeping my back against the window so the picture wouldn't be bleached out."

There was no shortage of shocking material. We see Millwall supporters throwing missiles at police as the chant in support of a convicted murderer: "Harry Roberts is our friend - he killed policemen." We are there when Sam Hammam boasts at a club dinner: We'll take anyone. We're f - ing sheep shaggers." We hear Darren Wells, hooligan and Right-wing extremist, lament: "It's a sad day when you get families at football. In the old days, it was much more fun."

At 5ft 11in and weighing 11 and a half stone, Williams is not, he admits, physically imposing. He faced some close calls, most commonly when the police confronted a gang he was travelling with. "I was searched six times, and that got scary. I was travelling with the Millwall hooligans - the most dangerous - from Euston to Nottingham one morning, and as we got off the train we were surrounded by a group of police officers who sent us towards others wielding metal detectors. I had to play a waiting game - I'd have been in serious trouble if it had beeped and they'd found my camera."

He whispered to the police that he was an undercover reporter and asked to be searched round the corner. "They did what they had to do, and then told me to go out and large it."

Unlike Donal MacIntyre, whose visibility makes covert investigations ever harder to pull off, Williams - credited merely as a humble assistant producer - intends to continue his quiet but effective form of journalism: he is about to go undercover for another year-long BBC project. So does he seek to topple MacIntyre - in defensive mode yesterday in an article berating his critics - as the face of BBC investigations?

MacIntyre has his respect, says Williams, but his personalised form of investigation is "just not my style". "Donal takes the audience along a journey with him, but I wouldn't be comfortable with that. I'm just a broadcast journalist."