The cameras caught every nasty detail. On a quiet night last autumn four men were hanging around the corner of Stirling and Bank streets in the centre of Airdrie, an old industrial satellite town of Glasgow. They had no obvious reason for being there, so the camera lingered on them. The first person to come round the corner was a youth who sensed their malice immediately. The thugs ran after him, but he was too fast.

The next person around the corner, just a few seconds later, was Alex MacKinnon (not his real name). He may have felt nervous, too, but before he could run one of the four asked him the time. The other three began to circle him. When he paused to look at his watch the first blow, a head-butt, was delivered. Others followed instantly. They kicked MacKinnon's head about like a football and left him lying in a pool of blood.

The whole incident was over in minutes. But for the camera, it would have been an investigative nightmare: one witness and no real clues. The police could have spent days interviewing locals, making appeals and conducting interviews. Identity parades, forensics and paperwork would have consumed more resources on the way to a lengthy trial that might not yield a conviction. The police would have had less than a 50 per cent chance of a conviction.

As it was, the cameras followed two of the men who were arrested within eight minutes of the assault. The others were picked up a few hours later. Mostly guilty pleas were tendered - there is little point arguing with video evidence - and the court case lasted just three days.

Since John Smith, then local MP and Labour leader, opened Airdrie's closed-circuit television system on 7 November 1992, the success stories have been legion. The original plan was to cut crime by 17 per cent and increase the detection rate by a similar amount. But police claim crime has plummeted by 74 per cent and the number of detections almost trebled.

There can be no mistake, this is the future of policing. It is Big Brother. Many British towns and cities, notably Liverpool, Bournemouth, Birmingham and Kings Lynn, are using closed-circuit television. Liverpool's surveillance system, opened yesterday at a cost of pounds 360,000, has 20 cameras that beam colour pictures to a team of security guards round the clock.

In Airdrie, however, a single hi-tech system operates without middle men. Day and night, views of the entire town centre are beamed straight into the police station.

As a result, police can arrive on the scene well-informed, make straight for the culprit and maintain radio contact with the control room to check developments. Endless questioning is a thing of the past. Police can also use the cameras to anticipate and avert an incident simply by arranging a presence. Fires and road accidents receive prompt attention. An ambulance was on its way to Alex MacKinnon, for example, before the assault was over.

Glasgow has learnt from its little neighbour and will soon install cameras to cover its city centre. CityWatch, to be launched in September, will be the largest police-monitored, centralised surveillance system in the country. The system's 32 cameras will cover more than 30 streets. A joystick offers 360-degree movement and a zoom makes it possible to detect eye colour from 400 yards. The system can also give photo-printouts of suspects. The city is investing pounds 500,000 in the project.

Arguments over civil liberties seem to have collapsed in the face of fear of crime. System 3, a polling organisation, found that 95 per cent of Glaswegians were in favour of CityWatch, 2 per cent were against and 7 per cent thought it infringed on their civil rights. Almost one-third said they would visit the city centre more frequently at night when the scheme was operating. Economically, that is irresistible. The Glasgow criminologist Jason Ditton says: 'Fear of crime is, in some ways, a bigger problem than crime itself.'

Little opposition canbe found among the city's pubgoers, despite their reputation for contrariness. 'Instinctively, I don't like the idea of being watched,' Elaine Etuc, an artist who was mugged recently, says. 'But I'm more worried about crime than a minor dislike.'

Others, such as Paul McCord, a copywriter, are more outspoken:'Civil liberty is abstract; crime is real. Our society is run by a chattering class, liberal dimwits who don't know diddley, but are precious about lofty ideals like civil liberties. They always want to 'understand' criminals. It's unique to western society to indulge criminals. Cameras are great because they catch scum.'

People smile approvingly while he rants. Several mention the fuzzy outline of James Bulger's killers. Yet unease about the political connotations of television surveillance hangs in the air.

Superintendent Graeme Pearson, who set up the Airdrie scheme and has been advising on CityWatch, claims the cameras preserve, not whittle away, basic rights. 'Rather than limiting people's liberty, they enhance their chance to enjoy public spaces. We are concerned about people's private rights, but, remember, cameras prove innocence as well as guilt.'

Even the Scottish Council for Civil Liberties, faced with the most invasive television surveillance in the UK, has bowed to its statistical success, but has asked for guidelines it has drawn up to be adopted.

'When panda cars came in, people said it will never be the same again; we're an army of occupation now,' Supt Pearson says. 'It was the same with police radios. Every innovation is seen as dreadful.'

Nevertheless there is a creeping sense that technology is taking over. Since cameras make such good economic sense, and are likely to become more sophisticated, we may be looking at a future where suburbs and even the doorways of homes are covered. How much longer before their interiors are, too? In Nottingham, under the auspices of the city council, tiny pencil cameras are to be installed in the front-door peepholes of homes. 'Youths get out on the bail merry-go-round and harass witnesses in their court cases, put filth through letterboxes or come round to assault them,' says Graham Chapman, chairman of the housing committee.

Critics of television surveillance claim that crime is not reduced by cameras, but merely displaced to other areas. Leslie Sharp, chief constable of Strathclyde, agrees that some crime moves outside the range of the cameras, but says: 'The more schemes we have, the better able we will be to concentrate on the displacement.'

The Local Government Information Unit has criticised the growing enthusiasm for television surveillance among local authorities, however, arguing that its success is unproven.

Claims of crime displacement serve only to promote television surveillance, however. One year ago barely a handful of councils were considering installing cameras. Now more than 300 are planning to do so, including Perth, a green-wellie and Barbour town with a low crime rate. Nearby Stirling and Dundee are installing systems, and Perth says it does not want their displaced crime. Already the question is not whether councils can afford to have television surveillance but whether they can afford not to. Big Brother is as good as here.

(Photographs omitted)