At least one person was arrested at a huge block party where hundreds of revellers ignored the coronavirus lockdown and social distancing rules.
Footage shows a massive crowd of mostly young people dancing to music played by a DJ, drinking, smoking or just hanging out at the rave about 350 yards from a police station in Harlesden, north-west London.
Police helicopters circled overhead for "hours", fireworks were shot into the sky and the party went on until 2am, according to neighbours who were kept awake by the noise.
The scenes sparked outrage on social media, where one local councillor said he was "embarrassed" and many people feared it would lead to a surge in Covid-19 cases in Brent, the borough with the highest number of coronavirus deaths in London.
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There was a huge police presence at the event, with video showing about a dozen officers being jeered as they try to make their way through the crowd at one point.
Neighbours said the party went on for hours and finally wrapped up around 2am.
Police stayed on scene until about 4am and helicopters were still circling overhead at that time.
Councillor Joshua Murray, a member of Brent Council, tweeted: "As Harlesden councillor I'm embarrassed of what's happen tonight. I will be working with community leaders to find solutions because at the end of the day my residents are suffering because few people want to have a dance during a week day when people have work the next day."
He added: "In area where kids who are not back at school can't go outside tomorrow cause there is broken glass everywhere. We need to do better."
A woman named Lisa tweeted video of the party and tagged police, Brent Council and local MP Dawn Butler.
She wrote: "Seriously? This is happening on Church rd Harlesden right now!! Can hear helis above. Guess no1 gets any sleep 2night. Selfish idiots."
As residents called on the party to be shut down a Twitter user named Bianca wrote: "Fireworks?? Really??? This Harlesden party is the biggest joke. What you celebrating??"
A woman named Dee urged the revellers to go home, adding: "Media outlets will just spin this and make it look like it is our fault that we are more likely to die from Covid because of our irresponsible behaviour and not because of racial inequality in this country."
Another user tweeted: "Not getting an early night with the helicopters hovering over Harlesden. Who decides to have a block party during a pandemic?"
A third wrote: "I’ve been put in the high risk category for covid19 so I have to self isolate and I feel trapped. Not because I can’t go out, but because I live in Church Road, Harlesden, an area where many people are ignoring the lockdown. Tonight’s block party hasn’t helped at all."
He later added: "4am and the last of the police vans are gradually leaving Church Road. Helicopters are still doing the rounds and I think some of the locals are more p***ed off with the helicopters than they are of the block party, which I think finished about 2am."
Another resident, named Miki, wrote: "F***ing hell, helicopters finally stopped after like 5 hours! Apparently a huge rave in Harlesden? Brent about to soar to the top of the covid charts again."
A police spokesperson said: "Police are currently in the area of Gifford Road, NW10, following reports of an unlicensed music event.
"Officers are engaging and dispersing a large group of people gathered in the area. There has been one arrest.
"The National Police Air Service (NPAS) is providing assistance."
It is the latest incident to fuel fears of a second wave of infections as Covid-19 cases and deaths currently trend downwards.
The fears were largely sparked by photos of packed beaches, parks and beauty spots, where social distancing was being ignored, in recent days during a spell of hot weather.
Police forces across the country have had to break up parties or large gatherings as people continue to flout the rules aimed at curbing the spread of the virus.
Earlier on Tuesday evening, six people were arrested after a brawl involving a large crowd of youths on north London's Hampstead Heath.
More than 50,000 people have died from coronavirus in the UK, according to the latest available data based on death certificates.
Brent has had the highest number of Covid-19 deaths in London and the sixth highest total in the UK.
There were 465 deaths registered up to May 22, according to the latest official figures.
Brent has the country's third highest death rate per 100,000 residents.