An intelligent CCTV system is being installed at one of the country’s busiest stations to protect the network from terrorists and vandals.

More than a year after trials were announced by Alistair Darling, the former Transport Secretary, the Daily Telegraph has learned that the sophisticated technology will be located at Clapham Junction Station.

The system has been developed by Agent Vi, a company which is responsible for the installation of 20 stations in Israel.

It is based on technology known as “Video Analytics”, which uses computers to spot unusual behaviour picked up by CCTV cameras.

While Britain has one of the most extensive networks of “spy” cameras in the world, very few are linked to any computers capable of processing the information.

But according to Gadi Talmon, Agent Vi’s founder, around 20 per cent of the UK’s CCTV systems could be linked to computers within about three years.

At Clapham Junction, the system is designed to spot intruders and unusual behaviour.

It is also being set up to detect graffiti within seconds of trains being vandalized.

This is done by recognizing how a train should look and then reacting when its appearance changes.

The defaced carriage is then highlighted on a screen. Then it would also be possible to identify the culprit, track his – or her – progress away from the scene, before alerting the police.

It is understood further systems are being considered by Transport for London and one is set to be installed at Paddington Station.

The number of CCTV cameras on the London Underground is set to reach 12,000 by 2010.

But until now there has been some skepticism over the effectiveness of a smart computer-driven network, especially when they are crowded.

However the industry, which is gathering at a conference in London this week, believes that interest will grow as the technology becomes more sophisticated.

One advantage is that computers’ attention never wanes, while tests have shown that a human being become 50 per cent less effective in monitoring a bank of cameras within about 20 minutes.

Advocates of smart CCTV argue that it provides cost effective protection for a network which cannot be sealed off in the same way as airports, where it is possible to screen every passenger.

Other mass transit systems, including those in New York and Rome, have already started installing their own versions of smart CCTV systems.

In New York, the system is designed to make it possible to send the emergency services to an incident within seconds.

The Rome technology is designed to react to unusual behaviour, such as somebody leaving a bag unattended or an individual moving against the general crowd flow.

But while the smart CCTV systems can detect somebody leaving a bag when a station is quiet, it is far more difficult to do the same at the height of the rush hour.