IT IS usually on Wednesday nights that they hold their clandestine meetings. There are a dozen of them, and they are known as the Twelve Just Men. Bands of vigilantes have sprung up in various parts of Britain, but there cannot be another like the Twelve. Their unique system for assisting the local police in law enforcement - uninvited, it must be said - involves a sharp-toothed ferret called Fred.

David Evans, founder and leader of the group, keeps Fred and two other ferrets in his back garden, feeding them on slices of raw liver to maintain their high level of blood lust. 'They're savage, especially Fred,' says Mr Evans, rolling up his shirt sleeve to reveal two nasty wounds. Up to now, Fred has not been used in the war against crime being waged at Newtown, in Powys, but the threat of the ferret sanction has been passed around.

'Our plan for keeping law and order is simple. Anyone we catch in the act of committing a crime we'll frogmarch off to the hills, where there's nobody to hear the screams,' he says. 'We'll hold him down and slip Fred into his trousers. It will be painful and terrifying, but it will teach him a lesson he won't forget in a hurry. He'll have the teeth marks to remind him.'

A rural Welsh market town, sprinkled with churches and chapels, Newtown is hardly the place one would expect to find vigilante patrols. But it is a fast-growing town. The population has doubled to 9,000 in 10 years. The Development Board for Rural Wales, which has its headquarters there, has attracted industries and people to the area by offering cheap factory space and housing.

Mr Evans, 47, a self-employed builder, formed the vigilante group after his television set was stolen. He never expected to see it again, but while watching a football match at a friend's house one evening, he suddenly realised that the set was his own. 'I knew it was mine by a cigarette burn on the top,' he says. 'I asked my friend where he'd got it, and he told me he had bought it from his sister. Both he and his sister are honest people. I knew they wouldn't be involved with stolen goods.

'I told a detective they could nab the burglar by working backwards through the chain. They just weren't interested. I tracked him down myself. But the police still wouldn't do anything.

'It was things like this that made me realise that the local villains were getting away with it,' Mr Evans says. 'They could go out burgling night after night without getting caught.

'The police are bloody useless. They go round the estates in their warm cars. If somebody was trying to get into a house, he'd just duck until the car went round the corner. If the police went out on foot, they might catch a few criminals.'

Before he started the group, Mr Evans lived temporarily in a caravan. He suspected someone was sneaking in and stealing small sums of money. He set a trap, wedging a shotgun with a string passing over the trigger so that it would fire if the caravan door was opened.

'I took the shot out of the cartridge and replaced it with rice,' he says. 'I didn't want to blow his legs off, just pepper him. But the police found out about it and made me dismantle it.'

He had no difficulty in recruiting members. Most of his friends and neighbours had also been the victims of crime. Now the Twelve Just Men go on patrol two or three nights a week, checking homes on the town's seven housing estates and keeping an eye on factories on three industrial estates. At their weekly meetings they share crime intelligence. Not much happens in the town without one of the group getting to hear about it. Burglaries and break-ins are discussed, and trouble spots identified for more intensive action.

One member of the group attends the weekly magistrates' court. David Evans says: 'The sentences handed out are pathetic. Known criminals with long records are put on probation or given community service. It's laughable.'

As well as trying to catch criminals, they have debated their own scale of punishments. At first they talked about breaking the fingers of anyone they caught committing a crime. But then they realised that Fred would be a more effective deterrent. 'If we caught a regular offender, we'd give him the ferret treatment and then hand him over to the police,' Mr Evans says. 'If it was someone burgling for the first time, we'd just let Fred loose on him. They would be too embarrassed to report us. But if they did and I was taken to court, too bad. I'd just put up with it.'

A criminal who showed true repentance might be let off with a warning. Mr Evans says: 'I went to the home of one young lad whose father told me he'd started doing a few jobs. I gave him a right dressing down. I warned him that if we caught him he could expect the full treatment - yes, Fred. He was shaking when he promised me he'd never step out of line again, and I don't think he will.'

Most of the vigilantes are factory workers who live on the estates and are fed up with having their homes raided and possessions stolen. They are family men, in their forties, with a respect for the law and a strong belief that what they are doing is right. They are all fit and can handle themselves. David Evans is a former wrestler who practises judo. 'We have no worries on the physical side,' he says. 'If the people we're after had a go at us, they would come off worst, there's no doubt about that.'

Until now, he has kept his identity secret, but he believes that there is no point in concealing it any longer. 'The police, the public and the local criminals all know me - and I know them. That's what makes us different from other vigilantes, and more effective,' he says. 'It's a small town, and we know the villains and they know us. They know they can't get up to anything without us hearing about it.'

Recently the Twelve wrote to 10 local residents, warning that the group had taken steps to 'eradicate nuisances'. After the letter went out, one recipient hastily packed his bags and left town. He has not been seen since. David Evans is delighted.

Newtown, part of the Dyfed-Powys police force, claims a higher-than-average 57 per cent detection rate for reported crimes. But the vigilantes argue that this is not good enough.

There are no statistics to indicate if the presence of the group has reduced crime. Official sources, such as the Chamber of Trade, think the presence of vigilantes gives the place an unfortunate image of being some sort of Wild West frontier town. However, there is a feeling among people on the estates that the burglars are not so busy these days.

People living on the housing estates are grateful. They have just asked David Evans to become leader of a newly formed tenants' association. And people with businesses who have been the victims of crime also say they feel more secure with the Twelve Just Men on patrol.

Adrian Jones runs a general store, the only shop on the Trehafren estate. He was burgled last January and pounds 1,000 worth of goods was stolen. 'I feel much safer knowing the vigilantes are keeping an eye on the place,' he says. 'You never see a policeman on foot round here. I've seen one in the three years I've had the store - and that was in the daytime, not at night when the burglars are at work. The vigilantes are doing a great job.'

Not surprisingly, the police do not approve of these activities. Chief Inspector Barrie Davies, based at Newtown, says: 'Leave the police and the courts to administer justice. If these so-called vigilantes carry out their threats, they could find themselves in far more trouble than the people they are directed at.'

The local MP, Alexander Carlile QC, is also worried, believing police work should be left to the police. 'My experience of vigilante groups in other parts of the country is not a happy one,' he says.

But the warnings from the authorities fall on deaf ears. The vigilantes are determined to carry on, claiming they have the popular support of the townsfolk. It looks as if Fred the ferret may yet have his day.

(Photographs omitted)