It was all over in 54 seconds. One moment the four friends were strolling home after a night out, the next they were nursing injuries inflicted by a knife-wielding assailant.
Another sad tale of crime and impunity in modern Britain? Not quite, for the incident last April in this town in southeast England was filmed from start to finish on surveillance cameras. Police were rapidly alerted; a suspect was quickly identified, apprehended, convicted, and sentenced. Case closed.
It's successes like these that are giving CCTV, or closed-circuit television, a good name in Britain. The technology has become popular and widespread, with the result that Britons are by far the most watched people on earth, with one camera for every 14 people, according to recent estimates.
More than 4 million cameras observe all aspects of life, from town centers to transport systems, office towers to banks, commercial zones to residential areas, restaurants, bars, and even churches.
In 1990, just three towns had systems. Now some 500 do, after a decade in which more than £250 million ($460 million) of public money was funneled into CCTV systems.
"The British public seem to like it," says Martin Gill, professor of criminology at Leicester University. "One of the great problems of our lives is crime and disorder, and people feel it can be tackled by having cameras on the wall."
But serious question marks hang over the technology and its dark Orwellian implications. Many cameras are hidden or not signposted, in breach of regulations. Several cases of abuse have been documented, raising fears of snooping or worse.
Civil liberty groups complain that the intrusive lens scanning for suspicious characters contravenes that pillar of civil society - the presumption of innocence.
Research meanwhile suggests that the camera systems may not actually deter criminals.
"One of the concerns about CCTV is that it can give a false sense of security," says Barry Hugill of Liberty, a civil liberties and human rights group based in London. "I suspect that the reason why people are happy with CCTV is that they say it makes us safer and stops crime. But we don't think there's evidence that that is the case."
Indeed, research has yet to support the case for CCTV.
A government review 18 months ago found that security cameras were effective in tackling vehicle crime but had limited effect on other crimes. Improved streetlighting recorded better results.
A new report being drawn up by Professor Gill for the government promises to be no more favorable in its assessment of CCTV as a crime-fighting tool.
"I have talked to offenders about this," says Gill. "They say they are not concerned by security cameras, unless they were actually caught by one."
Britain is a case apart from Europe, where most countries embraced the technology only in the late 1990s - and then with caution. According to researchers now preparing a report on comparative systems, France tends to limit coverage to high-risk locations and public buildings, while in Spain, surveillance is tightly controlled. In Austria, it is used primarily for traffic and transport systems. In Germany, it was severely restricted in public spaces until recently.
But in Britain, the public has had a soft spot for CCTV ever since it was used to dramatic effect to solve a wretched crime more than 11 years ago.
Most people can still picture the grainy footage of two juveniles leading 2-year-old Jamie Bulger by the hand out of a shopping mall in Liverpool. He was found dead days later. Without those images, experts say, police would have been looking for a culprit with an entirely different profile from the 11-year-old offenders.
"Since Jamie Bulger's case over here, the public see CCTV not as Big Brother but as a benevolent father," says Peter Fry, director of the CCTV user group, a 600-member association of organizations who use the technology.
"If you ask the public what they would like to do about crime, No. 1 is more police on the street and No. 2 is more CCTV," he adds.
The trend coincides with a growing culture of snooping in Britain, where speed cameras rule the highway, residents post their own cameras to spy on trespassers, and the favorite TV shows revolve around hidden cameras observing bland people lounging around.
But not everyone is reassured by the idea of lenses capable of reading a car license plate from half a mile away. Anecdotal evidence suggests the technology can be used for voyeurism, and concerns remain about who gets access to the tapes, which are typically held for a month before being erased.
In one case, a man's attempted suicide was caught on camera and passed on to television. Mr Lazell says he sometimes gets individuals calling on him to use the technology to spy on partners.
Prof. Clive Norris, deputy director of the center for criminological research at Sheffield University, told a recent conference that the technology "enables people to be tracked and monitored and harassed and socially excluded on the basis that they do not fit into the category of people that a council or shopping center wants to see in a public space."
Legislation requires authorities to clearly signal where cameras are in operation, yet as many as 80 percent are thought to break this rule.
Some cameras are being developed with face-recognition technology that raises further alarms.
"There are privacy concerns," says Mr Hugill of Liberty. "There are people who believe that we have fundamental human right to go about our business without being spied on. CCTV is spying. It's monitoring your every move."
Naturally, surveillance enthusiasts scoff at such logic, saying that operators will not be focusing on the average member of the public, but on anyone acting out of the ordinary.
For Mr. Lazell, it's a trade-off: a little liberty for greater security.
"All progress offers compromise," he comments. "Would you be prepared to take down all cameras in the Underground and let terrorists move about without being seen?"