Chief Inspector Roy Smith and his colleague are patrolling the streets of Lambeth in an unmarked car on a Saturday night.

It is a relatively large and diverse borough, and the types of crimes reflect this – each area has its own unique problems, from phone-snatching on the South Bank and sex assaults near the big clubs in Vauxhall, to drunken violence in Clapham High Street.

And, Ch Insp Smith says, Lambeth is one of the most violent boroughs in London – along with Tower Hamlets, Newham and Hackney - in terms of recorded crimes.

“It’s every day. There have been 13 stabbings and three drive-by shootings in the last two weeks,” he explains, adding that knives are seized on the streets of Lambeth on a daily basis – usually from teenagers.

Throughout the course of their shift calls come in for everything from no-damage road accidents to suspected murders.

The first few calls are not dramatic; a shooting which turns out to be a hoax and a man refusing to leave the pub.

But before the team had even set out there were 47 unanswered calls on the log and there were simply not enough police resources to attend.

“A large proportion of what we do is just keeping a lid on things,” he explains.

Another big part of policing is instinct, he says, explaining how the slightest hand movement can give away the fact that someone is carrying drugs, a slight change in posture at the sight of a squad car can expose someone up to no good.

And as though he had orchestrated it, Ch Insp Smith points out a small silver car with two men in that doesn’t look “quite right.”

He follows the car, and soon it starts weaving between lanes, trying to get away. A police ANPR check reveals the driver has good reason to escape – he is wanted for robbery.

Chf Insp Smith tails him, and when it becomes clear that the car is unlikely to stop, he pulls in front of a set of traffic lights, perpendicular to the road, blocking its path.

The driver is arrested, and booked into custody.

Explaining why he chose to follow the car, Ch Insp Smith says: “The driver didn’t have his seatbelt on, the passenger was slouched down.

“It was just a gut feeling, and that gut feeling was right.”

”Every day you drive into something, a car accident, or someone shouting in the street,” he adds.

“Not being able to switch that off – it’s one of the hardest things and most damaging to people’s home lives.

“You can’t walk away from a lot of stuff. It is your duty to go and sort stuff out.”

And as the night progresses, the police radio gets busier.

A man who is wanted over four separate crimes has been spotted, but is evading police. Squad cars block off every exit to the housing estate he has run into, and dogs are on their way to flush him out.

He’s on the railway tracks – the helicopter is scrambled. He stands on a railway bridge shouting at the dozen-or-so police officers below before finally coming down.

As the clock strikes midnight, the calls come in thick and fast.

A car is stopped and searched for drugs – two of the men inside have contraband on them, and one admits the cannabis has been concealed in his rectal cavity - he will have to be strip-searched.

There is a robbery on another housing estate, the victim has been set upon by a group of men, and is bleeding from his mouth and nose.

There is a stabbing – a man has gone into a takeaway armed with a weapon and knifed a member of staff in the head.

Someone has been glassed in the face in a pub; a nine-year-old child has gone missing; a man has smashed the windows of a bus and is trying to gain entry to the driver's cab; a patient in a mental health unit has attempted to take their own life and police assistance is required.

“We could have double the number of cops in Lambeth and it still wouldn’t be enough,” Ch Insp Smith says.

“HMIC [Her Majesty’s Inspectorate of Constabulary] described this as the most challenging policing environment in Western Europe.

”There are some difficult places to police.

”And we get called to everything – when there are no social workers available, no mental health workers, who do you call? The police, because we can’t say no.”