Sport On TV: Uncovering violent face of football's worst Nightmare

QUITE APART from the fact that it's illegal for men, I'm glad I'm not married to reporter Donal MacIntyre.

"Where are you off to today, darling?"

"Oh, I'm just driving a man called Nightmare up to a battle just outside Leicester. If he gets it into his head to confess to an awful crime that's still on the files, such as, oh, I don't know, slashing a policeman in the face and throat so he needed 68 stitches, I sincerely hope all my concealed cameras stay concealed and he doesn't discover I'm assembling material for Donal MacIntyre Undercover (BBC1, Wednesday)."

"Oh, that'll be interesting, darling. Could you bring back a nice bottle of vino, some olives and a jar of pesto on your way home?"

A Horizon programme on Thursday night suggested that multiple personality disorder is a figment of therapists' imaginations. But for a year and a half, mad man McIntyre dipped in and out of roles, working on all the installments of his series at once. He posed not just as a Chelsea Headhunter - a football hooligan crew giving their allegiance to the West London club - but also as an insider trader, fashion photographer, bodyguard and a worker in the care home from hell. At one point, he wrote this week, when one of the Chelsea big boys asked him what he'd been doing, he almost said, "filming".

In fact, you have to wonder if the Headhunters, described by a man from the Police Football Intelligence Unit as not "mindless thugs" but a "sophisticated criminal network", are all they're cracked up to be. After all, they didn't rumble MacIntyre, who makes a most unconvincing yob.

Apart from his sensitive good looks and his soft Irish burr, he was always dashing off to don a new mask. On the trip to Leicester, for instance, he drove them to the intended battle ground, the small town of Narborough, then dropped them off. Hardly the behaviour of the die hard.

And wouldn't his Chelsea tattoo, which he said he'd had for years, but for which he'd recently passed out on camera, bless him, have looked fresh? He just had the Chelsea badge on his arm. Jason Marriner, his root of entry into the Headhunters, is covered in them, one on his leg reading, "When we're good they never remember. When we're bad they never forget". One or two people this week complained that the programme was all mouth and no trousers, and indeed there's not much actual violence in it. But that misses the point: this is a portrait, unavoidably selective, of some of the key characters in this dark, depressing world.

The trip to Leicester in MacIntyre's hired silver Mercedes is the dramatic meat of the piece. When he realises that Nightmare, the Mr Big, is about to get in, he whispers, "It's Andy Frain!" As hard men say in films, you can smell the fear in his voice.

Perhaps the most chilling detail is that Nightmare is a natural comedian, with great rhythm and timing, who uses a Carry On mock-posh accent for his stories. And Marriner is an able sidekick. They discuss whether to ring the Leicester "general" to make arrangements for the rumble.

"Get the man out of bed," Marriner says. "Start terrorising him before he's even had a cup of tea and a shag. He won't be able to eat, he'll be physically sick."

They suggest a visit to the man's house, and Frain mimics a call on his mobile phone, in a high-pitched camp voice. It feels like A Clockwork Orange. "Open the door - your postman's arrived. Special delivery for Mr Dolby." He mimes a stab, in out, at his own heart.

He tells of a phone call to the Leicester mob before an earlier game: " `You'll be dead in two seconds. You come here five-handed - I take my hat off to you. We've got 50 geezers here - we'll rip your heads off.' I said, `You'd best trot along now, mate.' "

Then comes the confession that - with the police currently studying the film - could put Frain in jail. "We was laughing at him," says Frain in his Carry On voice. "He said, `You can't do that, I'm an off duty policeman.' I said, `Shut up, it's one o'clock in the morning, there's nobody about.' " - Frain makes two slashes, one to the face, one to the throat. "We was laughing," and he breaks up into a fit of giggles, holding his sides.

Almost the most depressing character, though, is 21-year-old Danny Walford, who idolises Frain. "It's good to get some time under your belt," he says as a court appearance looms. "Anyway, Frainie'll look after me. He knows so many people."

As MacIntyre drives to court, Danny looks out of the window and delivers perhaps the programme's most telling line: "I think going to football and fighting is an illness. I don't think you can just stop."

Danny wants to be like his hero Nightmare. This was the kind of programme that gives you them.