CCTV operators in Ely called police after spotting this man staggering around near a parked car in Chequer Lane and then watched in horror as he got behind the wheel and drove away. The footage shows the man shouting at his parked car; he then urinates be

CCTV operators in Ely called police after spotting this man staggering around near a parked car in Chequer Lane and then watched in horror as he got behind the wheel and drove away.

The footage shows the man shouting at his parked car; he then urinates before getting behind the wheel and starting the engine. All of this is captured on CCTV.

Unbeknown to the drink-driver, the CCTV operator has already alerted the police. As the car rounds the corner, again seamlessly captured on another camera in the next street, the police are waiting. The car is pulled over and the man is arrested and later charged for drink-driving.

The arrest was one of more than 10,000 headed by CCTV operators since the camera system was launched in 1997. The award winning team based at the Guildhall in Cambridge city centre have proved themselves a vital tool in crime prevention and detection.

After passing through four security systems, the converted darkened room is home to two walls of TV units, plus computer monitors for the operators to view and record whatever incidents are taking place on the streets above their heads.

PC Mark Arnold, based at Parkside Police Station, works closely with his police colleague Steve Roberts and the operators to find footage of crimes and isolate it for investigating officers, and the courts.

He said: "Last year we captured 800 of pieces of footage for investigations. Because we deal with so much footage, we have a detailed recording system for it.

"We don't just analyse CCTV footage, but footage for the air operations unit, traffic officers and voice recordings of 999 calls."

In the Guildhall there is a folder on his computer brimming with CCTV clips of old incidents which he uses for training purposes - such as this one.

The camera operators log every incident they see on a computer so the footage can easily be found. When they are recording an incident, they need to be able to switch from one camera to the next to follow the action.

This means they need a thorough knowledge of what each camera shows and where they are placed. Therefore, when an incident is viewed back, it's as if a rehearsed TV programme has been recorded with all the angles covered and the action flows.

This is vital for the identification of people involved, and so the footage is useful to any investigation, and potentially to a jury.

The CCTV system also has built-in technology which does not allow filming in homes and other private zones. If a camera looks up at a flat window a black square appears over the area where the window is and the camera automatically moves to focus on the street below.

Capturing the evidence where an operator can see an incident taking place is one thing. Searching CCTV footage from the city centre's 183 cameras within CCTVs area of observation for an incident which may or may not have been captured is where Mark's skills come in.

In a windowless room in Parkside Police Station sits a �14,000 computer which can read almost any sort of file.

"This is particularly useful for different CCTV systems used in shops, bars, clubs, hotels and other businesses," said Mark.

"The difficulty we can have is being given too much footage. For a straightforward shoplifting the officer will ask for the CCTV footage from the shop. Sometimes that might mean being given footage from 32 different cameras and days' worth of footage.

"We then need to find what's needed and that can be quite time consuming, but it's down to getting the best evidence."

Having an intimate knowledge of where all cameras are, and what they can see, is the key to successfully tracking down CCTV of incidents or offenders.

Like the CCTV operators, Mark knows which cameras someone will be picked up on if they run from one street to the next and therefore, which CCTV footage he should next check.

"Once we have found the person we are looking for on one camera, we are then able to follow them around Cambridge because we know where all the cameras are," he said.

"The operators are very clever and professional at what they do. They constantly look out for suspicious incidents.

"During the day the cameras tend to focus on shops and during the evening, on the bars and clubs."

When asked if looking through hours of footage for something that 'might have been captured' gets boring, Mark is aghast.

"Not at all," he said. "When you find what you are looking for, and it helps the investigation, it is all worthwhile.

"It doesn't matter what it is; a shoplifting, a rape, a violent assault or murder. It all gets the same treatment because it matters to that victim.