The Met: Policing London Season 4 is yet to be announced by BBC One

Homicide detectives investigate the murder of an elderly man in north London, we follow an undercover operation attempting to cut off the drugs supply in east London, and in west London police are on the hunt for Ealing's most wanted burglars.

In Brixton custody suite, a detainee has stripped naked and is refusing to come out of his cell and go to court. In another cell, a man has been brought in for threatening a supermarket cashier with a knife. In Croydon, a detective investigates a series of cat killings, bringing in a specialist in animal forensic pathology and criminal profiling experts from the National Crime Agency. While at New Scotland Yard, senior police officers plan the strategy for the year's anti-capitalist Million Mask March.

In Hackney, detectives investigate a spate of stabbings and encounter one victim who is reluctant to tell them anything. Detectives from the Met's Sexual Offences Unit try to gather evidence against a man suspected of sexually assaulting a woman with Down's syndrome, but with rape being one of the hardest crimes to investigate, they struggle to understand exactly what happened. The Met's dedicated robbery unit, the Flying Squad, use all their undercover surveillance skills in order to catch masked gunmen who have been targeting newsagents and supermarkets in south east London.

One of the Met's most experienced officers leads his team on a pursuit through London to intercept a car suspected of carrying a gun. Detectives Hitesh Patel and Paul Connelly, officers on Trident, the Met's specialist gang unit, work undercover in Harlesden to take down as many gang members as possible to stop the drug trade thriving on the streets of north west London. And the Met Commissioner, Sir Bernard Hogan-Howe, visits Islington and is confronted by the grieving family of Henry Hicks.

A recently qualified response driver in Westminster gets his first chase at 4am when a 17-year-old who has stolen his mum's car refuses to stop.

On the hottest night of the year, a huge impromptu summer party in Hyde Park results in chaos. Police come under attack and there is also a vicious stabbing. Homicide and Serious Crime Command hunt the suspect.

In Stratford, east London, a sergeant responds to the concerns of local residents by attempting to tackle the borough's prostitution problem.

In the past year, over 2000 officers have joined the ranks of the Metropolitan Police, tasked with keeping the streets of London safe for its eight million residents, 24 hours a day. Over 50 per cent of new Met officers are from outside London, and Yorkshireman Tom Hebblethwaite has his work cut out finding his way around the city streets. During his on-the-ground training he must achieve some vital goals, from making an arrest to learning to march before he can graduate and 'pass out' in front of top cop and fellow northerner, Commissioner Sir Bernard Hogan-Howe.

The streets of London are a challenge for even the most experienced police constables, and response officers Caroline Hay and Karl Davies are old hands at dealing with the ups and downs of policing the public in Camden, north London. While putting up with verbal abuse from angry buskers is just part of the job, it's protecting some of society's more vulnerable individuals that makes Caroline reflect on why she joined the service.

In east London, Detective Jason Weald is nearing retirement and must call on his years of experience to get to the bottom of the tragic death of a four-month-old baby. His team struggle to keep their personal and professional opinions separate as the quest to find justice in this emotional case divides the homicide detectives.

On an average night, the Met receives over 4,000 emergency calls, keeping London's 800 on-duty response cops busy from dusk till dawn.

Crimes thrives in the shadows, and in the residential streets of north London, a burglar has been caught in the act. It's down to PC Waz Din to literally talk him down when the suspect is found hanging from a first-floor window.

Eight miles away, on the busy streets of Soho, something sinister is lurking behind the bright lights. For the past two years, Detective Superintendent Kevin Southworth has been gathering evidence on the thieves and drug dealers exploiting the area. With the help of 400 riot-trained officers, he makes his move.

After dark, London's clubs and bars come alive, but as the punters spill out onto the city streets, it's up to the cops to take the abuse from the ones who can't hold their booze. And the long night can be a lonely time for those suffering from mental health issues. Constables Ian Gray and Christine Wratten rush to help two Londoners who are feeling suicidal.

Gangs are a major problem for police in at least 20 of London's 32 boroughs. Detectives Stuart McNaughton and Bob Dolce work for Trident, the Met's specialist gang unit. As increasingly younger boys and girls are being lured into the gang lifestyle, Bob and Stuart have focused on London's most dangerous gang, working undercover to take down its leaders and stop the lucrative drug trade thriving on the streets of south London.

Wealthy residents of Camden, north London, have been plagued by a wave of violent snatch-and-grab thefts by robbers using mopeds to evade police. Suspects are often only in their teens and cops are discouraged from chasing the criminals. Public confidence in the police is running low, and it's up to borough commander Richard Tucker to win back local trust and wipe out the problem.

Police constables Tim Dawes and Steph Mills have been patrolling the streets of Brixton for over five years and deal with knife crime on an almost daily basis. But nothing can prepare them for the shock of a vicious knife attack in broad daylight. It's up to them to try to save the life of an innocent teenage boy.

Mistaken identity leaves a young father dead and detectives struggling to catch his killers. Brixton CID hunt a violent sexual offender before he attacks again, and Notting Hill Carnival sees London's biggest police operation.

Documentary series filmed over the course of a year, following the officers of Britain's biggest and busiest police service as they deal with life, death, crime and its victims.

The killing by a Met officer of a young black man called Mark Duggan sparked the 2011 riots. Now an inquiry is about to decide if the killing was lawful, and Scotland Yard is anxious about renewed racial tension and more riots in London.