A man has been arrested on suspicion of murder and taken into custody, the Met said.
Primrose Hill was cordoned off on Monday morning as dozens of police patrolled the area and turned away families hoping to walk their dogs through the park.
Forensics teams arrived later in the day and a forensics tent could be seen at the crest of the park, while litter from Sunday night’s festivities littered the hillside.
The spot is among the most popular in the capital for those hoping to watch the London Eye fireworks, and one local woman said there were “hundreds if not thousands” of people there at the time of the attack, PA news agency reported.
She said it was “absolutely tragic and shocking” that a teenager could be killed on her doorstep, adding: “It’s not just a young people’s party – there would have been families with young children there, too.
“It would have been rammed. It’s not just locals – people come from miles around.”
Several others said they saw police searching revellers before they were allowed to leave the park, forming queues which took a long time to clear.
Another local, who wished not to be named, described the incident as “tragic but inevitable”, explaining he had made “hundreds” of complaints to police about anti-social behaviour in the park.
He said it had become a “party hotspot” with drugs and alcohol since the pandemic.
Gina Germano, a mother of two teenage boys who were at Primrose Hill at the time of the attack, said she had “warned” them about gangs there, explaining it had become “rough” since 2020.
Police described the area as “very busy” on Sunday night and urged those with information to come forward.
