UK police are monitoring more than 2,000 "drill" rap videos on YouTube in their war against London street gangs.

YouTube has deleted 130 videos at the request of police because of their links to crime. The gangs use YouTube to threaten rivals and boast about their attacks. And the police have used YouTube videos as evidence against gangs in court.

The stakes are high: More than 4,000 people a year are stabbed in London, mostly in gang conflict.

At least four rap groups are now banned by court order from performing or publishing their music.

Drill rappers are angry. "This is a threat to freedom of speech. Nobody in a free society should be imprisoned for words," one group says.

As soon as the dark blue Ford Mondeo pulled to a stop on Gordon Road that night, the 16-year-old boy standing at the side of the street knew he had made a mistake. He had been tricked into the rendezvous by an acquaintance. Driving the car was Isaac Donkoh, 21, a local rapper who also ran a gang in the Beckton E6 postcode area, a dreary neighbourhood in the east of London. It is best-known for being the home of the world's largest gasworks. Donkoh's crew that night consisted of four teenagers — two other 16-year-olds and two 14-year-olds.

Donkoh and his colleagues got out of the car, and forced the 16-year-old into the vehicle. Once inside they threatened him with a machete and tied two plastic bags over his head.

"I thought they were probably gonna kill me," the boy later told police.

In fact, they needed him alive. They wanted to torture him.

Over the next two hours, Donkoh and the others stripped the boy naked, beat him with a pole, cut him with scissors, forced him to swallow cannabis, and scalded his head and feet with boiling water. Then they made him call his parents and beg for £1,500 (about $1,900) as a ransom.

The gang filmed the whole thing on an iPhone. In April of this year, London Metropolitan police used it to secure convictions and prison sentences against all four young men.

The police were particularly interested in Donkoh's nascent career on the "UK drill" rap music scene. "Donkoh fronted drill music videos for his gang which goaded rivals and recruited boys as young as 14 to commit serious violence," Detective Chief Inspector Jim McKee said in a statement after the case was over. "We identified a direct correlation between his drill videos which glorified violence and shootings and stabbings on the streets."

The Donkoh torture case — and the drill music linked to it — is not an isolated incident.

'Operation Domain' tracks and controls London's drill rap scene, aided by YouTube

YouTube has removed 130 rap videos from its platform at the request of London police, who allege that the videos are weapons in a gang war that has led to hundreds of stabbings across the city in the last couple of years.

At least 20 convictions have been made in the Metropolitan Police's "Operation Domain" investigation of rap gangs, all leading to convictions. Eighteen received prison sentences.

The most controversial part of the campaign is the extent to which police are now monitoring — and banning — music videos on YouTube to track gang warfare and prevent attacks. The police told Business Insider that they are currently tracking more than 2,000 music videos in their database. "As of 21 June, the Met has submitted requests to YouTube to remove 154 of the 2,040 indexed videos, 130 have been removed," according to Detective Superintendent Mike West.

Two professional rappers, who go by the name Skengdo x AM, are now banned by a court-sanctioned "criminal behaviour order" from making music, performing songs, or publishing music videos without the approval of the police.

They received nine-month suspended prison sentences in January for an unauthorised performance of their music. "It [the CBO] was breached when they performed drill music that incited and encouraged violence against rival gang members and then posted it on social media," the Met told Business Insider. "The injunction was originally made against the individuals as they were members of a gang in Lambeth and were associated with the escalating gang violence in the borough."

A further 11 less well-known rappers in groups linked to the 1011 and W12 gangs are also banned from performing without police permission.

An official for YouTube confirmed to Business Insider that the company was cooperating.

"We have developed policies specifically to help tackle videos related to knife crime in the UK and are continuing to work constructively with experts on this issue. We work with the Metropolitan Police, The Mayor's Office for Policing and Crime, the Home Office, and community groups to understand this issue and ensure we are able to take action on gang-related content that infringe our Community Guidelines or break the law," a spokesperson said.

The music bans raise obvious issues around censorship, free speech and creativity: Should the police have the power to ban the mere performance or publication of music? Is YouTube right to cooperate?

London's gangs are responsible for thousands of stabbings per year

From the police point of view, Operation Domain is a straightforward law enforcement action. The scale of London's gang wars is terrifying: In the 2018-2019 year ending in March — the most recent numbers the Met has published — there were 4,277 stabbings. The previous year there were 4,732. There were 122 homicides of all types in the most recent year, an indicator that stabbings tend to leave their victims alive.

There were more than 1,300 stabbings in London, and 80 murders, in the first six months of 2018 alone, according to a Sky News investigation. "The overwhelming majority of these are gang-related," Sky's Andy Hughes reported. The conflicts are conducted between dozens of tiny postcode-based crews. It's not a "war" as such. More like a chaotic free-for-all, conducted in continuous fits and starts.

The police say that they are simply responding to criminal threats and incitement. The fact that the threats rhyme and are delivered via slick videos on YouTube makes no difference, police say.

"Gangs try to outrival each other with content - what looks like a music video can actually contain explicit language used by gangs to threaten each other. They can include gestures of violence, with hand signals suggesting they are firing weapons and graphic descriptions of what they would do to each other," superintendent West said. "The speed at which an online disagreement can escalate into violence, often very serious violence, is staggering."

Slow, ominous beats and lyrics about violence, revenge, and demands for respect

The police are focused on a single genre of music: UK drill.

Drill was invented in Chicago sometime around 2010. But it has been taken to another level entirely in London. UK drill is characterised by slow, ominous beats with a cinematically gloomy melody looped on top. Rappers deliver their lyrics rapid-fire, in strong London accents. The songs are predominantly about gang violence, revenge, and demands for respect.

UK drill videos also have signature visual tropes. They're often shot on a low budget, with dark, shadowy backgrounds. The performers pose in masks and bandannas as if they fear being identified, and they flash various threatening hand signals. Conspicuously absent are the wealth symbols — jewelry, cars, swimming pools — that populate mainstream US rap videos.

The whole scene looks like a fantasy of what a scary London street gang might look like.

The police say that, in fact, they are London street gangs — who are genuinely scary.

It is not clear where the rap groups end and gangs begin

For instance, five members of the Notting Hill-based group 1011 were arrested last November while carrying three machetes, a large knife and two baseball bats, according to The Guardian.

They were sent to prison in May 2019 for conspiracy to commit violent disorder, receiving sentences ranging from one year to three years and six months. "The gang pleaded guilty at Kingston Crown Court on Wednesday, 16 May, after arming themselves with machetes and baseball bats to take on a rival gang last November," West said.

The 1011 gang/group is now banned from making music for three years without police supervision.

"The gang can meet in public to make music if they have authorisation from police. They must notify police of any new official music videos (i.e. filmed by media companies) they feature in within 24 hours of publication. They must also provide police with a list of their official videos that are currently unpublished so they can be taken out of circulation if they breach the conditions of the CBOs," West said.

"He called other gang members who quickly arrived and a large group, armed with large knives, swords and wooden sticks, launched an attack"

Prior to that, eight members of the W12 gang in Shepherds Bush were sentenced in September 2018 for their involvement in a melee in which one of their members was stabbed in the back, leaving him with serious injuries.

One member had spotted members of a rival gang from Kensington and Chelsea on their turf in the White City section of Shepherds Bush.

"He called other gang members who quickly arrived and a large group, armed with large knives, swords and wooden sticks, launched an attack on the three males," West told us. "They chased them through the area and the incident ended in a violent confrontation during which one of their own - [a 16-year-old] - was stabbed in the back."

Both gangs evaded the police that night but, astonishingly, the Kensington and Chelsea crew made two drill videos describing the fight. The lyric to one song went, "Wit 2 shanks up creep up like luga leave man cut now the 12s all hot." The police were able to identify the gang member who had carried two knives ("shanks") that evening. "The 12s all hot" is a reference to the police presence that moved into the W12 postcode area after the clash. Another member uploaded a video to his Instagram account while he was awaiting trial. They were all convicted and given a range of sentences, the longest being four years.

The cases put police officers in the unique position of being music critics who make legal judgments about what song lyrics really mean. The lyrics and the videos were used as evidence to convict the men. "They [the police] presented evidence to the courts of a number of drill music videos to demonstrate the tensions between the groups," the Met said in a statement given to Business Insider.

"We are not trying to prevent young people's artistic expression but when music is being used to encourage violent attacks we must act, as the public would rightly expect us to do so," the Met said.

Skengdo x AM are now all-but banned from performing unless they are willing to go to prison

The most controversial rap ban was the CBO affecting Skengdo x AM. They were previously the subject of an injunction on their music due to their association with the 410 gang in Brixton, South London. They played a gig at the Koko venue in Camden, capacity 1,400, in December. The police said the concert breached the CBO. It "was breached when they performed drill music that incited and encouraged violence against rival gang members and then posted it on social media." The pair — real names Terrell Doyley and Joshua Malinga — were given nine-month suspended sentences.

Skengdo x AM are now all-but banned from performing any of their music, unless they are willing to go to prison. Neither performer made himself available when Business Insider reached their manager.

Civil liberties campaigners such as Index on Censorship and Liberty are appalled.

Another drill group, Krept and Konan, started a Change.org petition demanding that the police stop using the Serious Crime Act to prosecute drill artists. (The band did not immediately return a message requesting comment.)

"The police are using laws made for terrorists and sex offenders to criminalise musicians who sing violent lyrics," their petition states. "It means that the police no longer have to prove any link between an artist and a specific act of violence to secure a conviction for 'inciting violence'. This is a threat to freedom of speech. Nobody in a free society should be imprisoned for words."

The police seem to be aware that they're treading into civil rights territory.

In an email, Detective Chief Superintendent Kevin Southworth told Business Insider, "We're not in the business of killing anyone's fun, we're not in the business of killing anyone's artistic expression — we are in the business of stopping people being killed. When in this instance you see a particular genre of music being used specifically to goad, to incite, to provoke, to inflame, that can only lead to acts of very serious violence being committed, that's when it becomes a matter for the police."

Donkoh and his crew —the boys who tortured the 16-year-old in Beckton — did not receive CBO bans on their music, however. They were not needed.

Donkoh will be in prison for the next 12 years. The other four received two-and-a-half years apiece.