To get to your table, five sets of reinforced steel doors must be laboriously unlocked. As you arrive, your mobile is confiscated by a big bloke with a crew cut, and you're asked if you are carrying any metal cutlery or excessive amounts of tobacco. Crumbs. And I thought Nobu was hard to get into.

This, though, is soon to be the place to eat: High Down Prison in Sutton - a Category B establishment containing 740 inmates detained at Her Majesty's pleasure. Here, catering manager Alberto Crisci is set to open a 100-cover restaurant called Clink. It will be staffed by prisoners (your waiter may be busy serving the soup course, but he could also be serving six to eight for aggravated burglary) and boast a proper menu, complete with pan-fried John Dory, paupiette of chicken with spinach mousseline, roast turbot with broad beans and pancetta, and lavender mascarpone served with spun sugar and figs marinated in Chianti. And definitely no porridge.

Visiting a prison is a sobering experience. Even the most streetwise newcomer can't avoid getting a touch of the Jodie Fosters: all those doors, all those keys, all those bars on not enough windows. While the grounds are neat, with their orderly beds of Polyanthus, there's no getting away from the fact that it's a trifle grim. But Crisci, bless him, has high hopes for High Down.

'It's not just a gimmick,' he insists. 'For it to work, it must be a real restaurant, not a dodgy prison mess. I want it to look like Gordon Ramsay's bloody restaurant! It's going to be a dreary walk through the prison, but it will be an oasis once you get here. Staff will be smartly dressed, even if they have tattoos.'

At first, diners will be welcomed into Clink on an invite-only basis. Heads of business, food industry powers, anyone who might talent spot inmates or raise the profile of the endeavour. They will enter the restaurant through an unmarked barred door. Within, however, the transformation will be total. What is currently a store-room will become an upmarket venue with ambient music and well-dressed tables. The open kitchen - complete with a handsome £4,000 hand-built Molteni stove - will be operated by prisoners who have trained by Crisci.

'What they're in here for is immaterial to me,' he shrugs. 'I want people who eat at Clink to ask, "Have you got anyone coming out soon?" I want people to hire these guys once they're released, not ignore them because they've got a criminal record.' Think of Crisci as Jamie Oliver with locks on. He recently won BBC Radio 4's Food and Farming award, an accolade previously bestowed upon Oliver and dinner lady Jeanette Orrery. Beyond arming ex-prisoners with the NVQs to do battle in the job market, Crisci is engaged in a grander social experiment. He's feeding decent grub to the cons. With a budget of £1.68 per man per day, the 1,500 meals that pass daily through these kitchens are all made from proper, fresh ingredients, using produce grown in the prison garden or on prison farms. 'We don't buy any frozen veg at all,' says Crisci with pride.

'Some of the men who come in here have to be weaned off processed food,' he says. 'They're used to kebabs, burgers, pies and chips. They've never eaten aubergine or octopus. Our prisoners have tried Parma ham, herrings, trout ... anything I can get at the right price.'

While Crisci sees it as a matter of principle, there is now evidence that a nutritious square meal can bring out the best in your average felon. Bernard Gensch, researcher at Oxford University's Department of Physiology, found recently that adding vitamins and nutrients to the diet of young offenders at a maximum-security institution in Buckinghamshire cut offences there by a quarter. The greatest reduction was for serious offences, including violence, which fell by 40 per cent. Now there's food for thought.