Laugh? I thought they'd never let me out

Eye witness: Prison comedy

He works the crowd like a pro, milking the laughs. Ambrose Mendy, who managed the world champion boxer Nigel Benn at the height of his powers, is spinning a yarn about the day his boy fought Chris Eubank. This is the first time Mendy has done a stand-up routine in front of a live audience, but you can't tell. The delivery is polished, his mimicry of the two fighters is spot on, and the gags may be about as subtle as the Dark Destroyer's right hook but they are hitting home. "What the fuck is it with fighters and a lisp?"

The massive men sitting in the front row, who have all just come from the gym, bellow their approval of a character who was once called the British answer to Don King. "We was there," says Mendy, recalling his glory days at the start of the Nineties. "Trust me we was there." The audience loves his swagger, but even if it didn't nobody could walk out. There are guards everywhere. This is not a comedy club but a high-security prison.

Mendy has just been on an intensive, eight-day course in how to be a comedian, learning the stagecraft that gives him poise as he stands under the spotlight in a training suit and a pair of boxing gloves; but it is not as if he had any other pressing engagements. He is not a visiting performer but a fellow inmate.

So are all but one of the other performers on the bill at this special show in Her Majesty's Prison Brixton. Of all the shows in town, this must be the hardest to get into: invited outsiders have had to pass through several locked chambers before being led deep into the prison, past the basketball court that is enclosed and sealed with barbed wire, and up narrow stairs to the chapel where a stage has been built.

The performance is the finale of a course run by the Comedy School, whose associates include the critically acclaimed stand-ups Arnold Brown and Felix Dexter. "We use comedy as a way of analysing issues around peer pressure, cultural contexts, social behaviour, and professional experiences," says the company, whose work is supported by the Arts Council and the National Lottery.

The prisoners gave up visits and other rights to attend five hours of classes every day. They had to learn to trust each other and be vulnerable with their peers. The process was painful at times says Harry, 39. "It has taught us how to accept positive criticism. On the wing there is no such thing, if somebody says something it turns into a confrontation right away."

Keith Palmer, who has led the course and acts as compère, says: "This is about self-discovery. We need to hear the true voice or comedy doesn't work. We also want to tell them that comedy is an honest way of making a good living, if you've got the talent and the application to learn the right techniques."

So how many of the 11 have what it takes to succeed on the outside?

"Oh," he says, "half a dozen."

That seems a lot, but there's a punchline coming. Seriously?

"Seriously? No. This is comedy."

Talk of building self-esteem seems a bit unlikely to anyone who has seen a tearful first-timer flee the stage after being demolished by hecklers, but Keith says this is different. "They have already taken up this challenge and seen it through. Whatever happens I know they will not jump off the stage and punch somebody in the face, and believe me that is a big step forward."

The small audience includes the families of the performers and other inmates. "There are no murderers or rapists," says someone from the prison service. "There's one or two for aggravated burglery, maybe, and theft or fraud."

Rudy Lickwood, a professional comic, ends his warm-up routine with an appeal to the audience not to be upset by what they're about to hear. "Don't let nothing offend you. We're in the world of comedy."

There is little heckling. The nearest we get is when leering Dave from Liverpool asks: "What's the best thing a woman can do to you, guys?" There are a dozen women in the house. One speaks for the rest: "Let you live!"

Most of the jokes would make Bernard Manning blush. "I'm having to fill in tonight for a gay magician," says Spike, shuffling on stage like the Seventies acidhead he may have been. "He vanished. Disappeared with a poof!"

The star of the show is Mendy, 49, whose routine hints at a change of career when he gets out. A former adviser to Linford Christie and other leading sportsmen, he has been jailed before, for fraud, and was sentenced to six months for burglary in March.

But the best line of the evening isn't spoken on stage. It is shouted from the back of the room when the governor stands in the spotlight at the end, beginning his thank-you speech with: "Ladies and gentlemen, what can we say?" The answer comes from a voice in the darkness: "Let 'em go!"