Watching them watching you – The amazing dramas captured on Leeds CCTV

They find nothing and let him go. He heads off towards the Market. However, remotely operated cameras continue to monitor him and record him taking the purse out of his pants and emptying the contents into his pocket, before throwing the purse into a bin. Seconds later, he is picked up again by officers and arrested. He thought he'd got away with the theft, but didn't reckon on live CCTV following him through almost every inch of the scenario.

The man, a well-known thief-about-town, was sentenced to an 18-month community service order and paid compensation to his victim.

On Hallowe'en, amid the good-natured ghouls and pumpkin-headed revellers in the city centre, a disturbance erupts outside a night club when a fight develops between a group of men. The CCTV camera in the street shows how bouncers from the club join in with fists and feet as the booze-fuelled melee develops. Meanwhile, officers are called to another street incident, where a man is causing trouble outside a different club. When police officers try to restrain him, he resists them with almost superhuman strength, and appears to be under the influence of drugs. Bystanders start to dance, sing and take

photographs as officers struggle to grapple with the man.

In both of these incidents those involved in decisions about whether to press charges found video footage invaluable because complicated and heated situations involving groups of people, especially where alcohol or drugs may be involved, can be very difficult to piece together. There can be as many different stories as there are witnesses.

CCTV gives an impartial view, and often provides high-quality pictures of the scene before emergency services arrive, images that are good enough to use as evidence in the prosecution of hundreds of criminals each year. It's also used to rule out those who might somehow have become implicated but were not in fact involved. There are 385 high-spec video cameras positioned around Leeds city centre and a few suburban "hot spots" in the area, including Wetherby, Harehills,

Armley, Morley, Otley , Yeadon, Horsforth Garforth, Kippax, Swillington, Rothwell, Halton and Crossgates.

On a Saturday teatime in the control room for the council-run Leedswatch 24/7 surveillance service, a team of six operators is on duty. They are stationed in front of a wall of 39 CCTV monitors. Each provides broadcast quality pictures from cameras which are programmed to change position at intervals.

The monitor switches between cameras and the cameras themselves reposition themselves in a cycle. If something that seems unusual merits a closer look, the view from a particular camera can be switched down on to one of a pair of desk monitors right in front of the operator.

Each highly qualified and experienced member of the team is familiar with the lie of the land around each camera, and also with the sequence of the cameras in relation to each other – a skill that's vital in following a car chase, for example.

From his or her desk, the operator can move the camera remotely to capture an incident from a different angle, or seek a close-up of the faces of thugs breaking into a car, feral children starting a fire, a transaction between drug dealer and customer, or the getaway route of a bag snatcher.

They often use the camera to spot and keep an eye on a vulnerable person – a lost child, an unconscious drunk in a doorway, a mental health patient or elderly person who has gone wandering – until emergency services arrive to help them. The cameras have frequently assisted in preventing an individual from committing suicide by jumping from a bridge.

Plummeting temperatures seem to be ensuring that there's not a great deal stirring in the street just now – but that will all change between 3am and 4am, when four or five thousand people, some of them with a great deal of alcohol inside them, will exit the city's clubs and head for taxi ranks or takeaways. Many cameras will be trained on known trouble spots.

"Young women can be every bit as bad as the men," says deputy operations manager Derek Pearson. He shows me footage of a fracas involving a group of shrieking women who set about another female, pinning her to the ground. While one sits astride her, she is beaten, kicked and spiked with stiletto heels.

The control room listens in to police radio messages; staff here can use cameras to watch incidents until police arrive at the scene and continue to monitor from afar. West Yorkshire Police control room is seeing the same pictures as Leedswatch, but can't manipulate the cameras. If the Leedswatch team spot an incident somewhere that they think needs police presence, a call is made to police operations, and the incident is followed to its conclusion in case footage is needed later.

A female operator gets a call about a half-naked woman who is thought to be wandering about in an area she is watching. She assesses the view from every camera in that neighbourhood but to no avail. Now and again during the evening a request for video comes in by fax from a police station in the area.

Each morning police officers come in to view tapes that might help with ongoing investigations. Footage not being used in an ongoing

investigation can only be kept for 31 days before being erased. "We haven't lost a case yet where CCTV evidence has been taken to court," says Derek Pearson. "Often, when a suspect hears that video evidence is going to be used, they plead guilty and save a lot of time and money that would otherwise have been spent in arguing the case."

In 2007, evidence from CCTV cameras provided vital evidence in 3,000 convictions for criminal offences which range from

anti-social behaviour to murder.

As the last shoppers make their way home, a group of lads play football in Briggate, and drinkers pop in and out of pubs for a smoke. They're doing no harm, and the camera doesn't even get a close-up although it could get a decent facial image from a 500ft distance, if required. Strict protocols on the operation and use of CCTV mean cameras may not linger on people or take close-ups unless there is reason to suspect wrongdoing.

If something that's possibly suspicious is spotted – two people standing close together in a suburban garden late at night in an area known for drug-dealing, for instance – then the camera can zoom in but must withdraw after a few seconds if nothing untoward is seen.

In one case, a police radio message directed the operator on to a house where a report had been made of a female allegedly being beaten up by her partner. Unbeknown to the woman, the all-seeing electronic eye had earlier recorded her getting another woman to beat her about the face so that she could then call 999 and blame the partner she presumably wanted to get rid of. It was only after the investigation of the emergency call and the arrest of the male that officers examined footage recorded earlier and discovered the real cause of her injuries.

A long-standing male member of the team describes the satisfactions of the job: "You develop a sixth sense. You can tell at a distance if someone is about to do something, purely by watching their body language. Even in a crowd you can spot it. It's frustrating when you don't quite get the pictures you need because someone is running away from the camera. But knowing that you are part of a team that's making the city safer is great."

Officers are given targets in terms of numbers of arrests. A newish member of staff might be expected to hit 10-15 a month, and for very experienced staff the objective will be 40.

A female colleague says she copes with the more traumatic scenes by distancing herself. "I tell myself I'm watching a film... But we do have a good counselling service, if needed. You might see terrible stuff sometimes, but it makes you feel good to have a part in bringing people to justice."

Does she think having hundreds of cameras are intrusive? "No. If people haven't done anything, they have nothing to worry about."

One officer arrived back from holiday and was reviewing footage from the night before when he realised that a young man being battered in the street by a gang of six was a member of his own family. The whole incident was caught on camera and three arrests were made.

Six years ago, 14 cameras were installed on the Halton Moor Estate in East Leeds, as part of a wider strategy to reduce rampant anti-social behaviour and crime rates. "There were many boarded up houses back then," says Derek Pearson. "People didn't want to live there. But a survey carried out 18 months after the cameras were first installed showed a 48 per cent overall reduction in crime and a 65 per cent reduction in burglaries."

After initial Government funding for 60 cameras in 1996, they were installed around Leeds at a rate of about 20 a year until 2008. No-one is saying CCTV cameras alone cut crime, but Mr Pearson says councillors and politicians of all hues are very keen to see them used. Running Leedswatch cost council tax payers more than 1.5m in the year 2008/2009 year.

The positioning of new cameras is often linked to a growth in crime in certain spots. For example, a camera already monitored the cash machines next to the entrance of Fish Street, an alleyway close to Leeds Market, but one was actually installed in Fish Street itself after repeated incidents of women posing as prostitutes luring men who had used the cashpoints up into the dark street where men were waiting to mug them.

Derek Pearson admits that part of the effect of CCTV presence is the displacement of crime to areas where there is less surveillance. "That will happen, unless you put cameras everywhere. But cameras are actually a last resort, installed only after research into crime figures, truancy statistics, social services reports and other data.

"And CCTV isn't a silver bullet – it's part of a wider raft of measures to cut crime and keep people safe."

Coun Les Carter, chair of the city council's Safer Leeds team, and executive board member for community safety, said that in the period 2005-2008, a 32 per cent reduction in crime had been achieved in Leeds "helped in no small part by the city's CCTV operation."

CCTV facts and figures

Research published last month revealed there are nearly 3,000 cameras watching the public in the Yorkshire region.

n Hull City Council has installed 524 cameras, the most of any authority in England. Leeds has 385, while Sheffield has 377.

Nationally the number of CCTV cameras has risen from 21,000 to 60,000 in the last 10 years. Portsmouth and Nottinghamshire Councils are in control of the most cameras with 1,454 each.

n The Shetland Islands has 117 cameras, which is more than the San Francisco Police Department.

n When installation, maintenance and operating costs are taken into account, the bill for operating one camera can be up to 3,000.

n Data from Big Brother Watch.