I met up with him again in Camden High Street. It was hard to recognise him for the man he had once been. Liver-sick blind in one eye, dressed in tattered clothes, his days are now spent drinking cheap wine in the 'boneyard' (graveyard) in Pratt Street. By night he sleeps in a flea-ridden doss house.

Once, three decades ago, things had been different. Then he had been the No. 1 contender for the Scottish lightweight title. Money, women, fast cars and flash clothes came easily to him, until he started to lose in the ring. Before long, he'd lost everything. Now Scotch Billy sits on a bench swigging from a bottle and, as the wine starts to hit him, it ignites an old spark. Suddenly tiger-like, he throws a few phantom punches, and for a moment you can see the class he'd once been.

If he could only have a few days' training, he says, and the fare, he'd try his hand at an unlicensed bout, in the West Country maybe, or Essex. He turns to me: 'You look trained to the second, though. You could go in and take on a few . . .' 'Maybe as a spectator,' I say.

Two weeks later, it's a cold wet night with the mist coming in from the marshes, when I turn up at the pub Scotch Billy described. Eddie, who sells used cars and scrap metal, is waiting for me. He has a fat face and a scar just under his right eye. He wants to check my credentials. I buy him a drink, and it doesn't take long for him to give me the OK. 'Just wanted to make sure you weren't the law,' he says.

I pay him a tenner and we take off through the wastelands of Essex, driving down desolate little roads past old warehouses with rotted awnings and rusting machinery. We are among the last to arrive. The cars are parked at the back of a derelict meat-packing warehouse. There are about 500 people here. Old packing cases line the walls. In the centre of the massive building, a ring has been erected. The boxers, advertised as Stackpool and Smith, stride in. They are both six-foot heavyweights with brute craniums and square jaws.

It seems like any other professional event. But it isn't. They have trainers and managers - flashy blokes in pinstripes - but these days they could never fight professionally. Once, like Scotch Billy, they could have been champions, but today they're barred, either for being crooked - taking one dive too many - or on medical advice. One more punch, they've been warned, and they could be out of the picture altogether. But they can't let it go. Tonight there's more at risk than the purse of pounds 1,500. The referee goes through the motions by checking their gloves, and offers the traditional words to keep it clean.

'We who are about to die salute thee,' growls Eddie at my side, then surprises me by repeating the dictum of the gladiators of Ancient Rome, in Latin: 'Morituri te salutamus]' The bell has hardly sounded when the fighters hurl themselves across the ring at each other. Landing in a clinch, they begin banging their heads into each other's faces with sickening force.

This evening's fight will be hard. It's in the air. Every one of the spectators adds their own unit of barely contained aggression, fuelled by cans of Special Brew. A few fishwives are here, and the gangsters' molls, faded, jaded blondes living, like the boxers, on past glories.

In the ring, it's become painful to watch. With a sullied kind of honour, Stackpool backs off. Then Smith lunges forward, bringing his head up into Stackpool's chin. The crowd roars, and Stackpool lurches backwards with a whiplash of blood. His nose is all over his face. Another clinch. The referee just manages to prise them apart, and that is the last resemblance to a professional boxing match.

From now on, the referee is superfluous. Early in the next round, Stackpool brings his knee up into Smith's groin. But Smith, instead of taking a dive, retaliates by grabbing Stackpool around the neck and sinking his teeth into his cheek. Stackpool, blood splashing from his torn face, begins retreating. Suddenly he stops. Standing flat-footed, he throws a wild punch that lands luckily. Smith staggers, more from surprise than the force of the blow, and Stackpool is on him. A vicious upper cut fires Smith on to the ropes, where he becomes entangled. The crowd bays.

As Smith tries to wriggle free, Stackpool begins butchering him at leisure. He plunges his thumb into Smith's left eye, gouging at it, then throws one last vicious hook. Smith stiffens, slides free from the ropes and falls unconscious to the canvas. As Stackpool raises his right hand, two of Smith's teeth can be seen embedded in his glove. Smith is still unconcious as he is carried from the ring. He obviously needs medical attention but, since it is an unlicensed fight, no doctor is present. It is standard fare, Eddie says.

For me, this travesty of the art demonstrates why boxing must never be outlawed, despite the clamour whenever a tragic accident occurs in the ring. The sport must be kept under scrutiny; the participants must be made to observe a strict code, ensuring that boxing retains some measure of skill; and first-class medical attention must be available. By banning boxing, we would be driving it entirely from the spotlight and rigour of public control.

That night, at least, Stackpool was a champion again. To the victor, the spoils. But it may be only a question of time before his next opponents are the likes of Scotch Billy, and the stakes are no higher than a bottle of cheap wine.

The writer, author of the novel 'Streets above Us' (Paladdin pounds 4.99) and 'The Grass Arena', his autobiography (Faber pounds 4.99), is seeking a publisher for his sequel, 'The Glass Cage'.