A suspected knifeman was chased down and “sat on” by partygoers following a fatal stabbing in north London.
The victim was found by guests at a birthday party held at the Old Edmontonians FC clubhouse, Enfield, shortly after 20:10 BST on Saturday.
Despite treatment, the 29-year-old man died at the scene.
A 40-year-old man was arrested after he was “pursued and detained” in a nearby field, police said. The suspect is currently being treated in hospital.
Police said the attack is not thought to be connected to the event or the football club.
The clubhouse manager, 60, who asked not to be named, said a man came running over towards the party from a nearby playing field and “called for help” before collapsing.
A second man could be seen further back on the club’s football pitch appearing to “goad” the guests.
Partygoers slowly approached the suspect “somehow got him on the floor and sat on him until police came,” the manager said.
A “corporate birthday party” had hired out the clubhouse for a group of 70 people from Romford, including some children, the manager said.
“When I came to the door there was just a group of people around [the victim],” he continued.
“The woman from the bouncy castle was giving him chest compressions.
“I was shocked by it. You read about these things but you don’t expect it to be happening right in front of you.”
Det Ch Insp Paul Considine, of the Met Police, said: “There was party taking place at the nearby Old Edmontonians FC clubhouse on Saturday evening. Lots of people were out and about.
“Members of the public pursued and detained a male suspect following this attack in a nearby field. He was subsequently arrested by police.”
The deceased’s next of kin have been informed and officers are not looking for anyone else.
The Met said specialist forensics teams are still at the scene of the attack.