Officers were called at 5.54pm on Monday, 31 May to Montrose Park, Edgware, following reports of a group of males fighting.
Officers responded and found an 18-year-old male suffering from a stab injury in a tennis court area.
He was treated by London’s Air Ambulance and London Ambulance Service at the scene. Despite their best efforts, he was pronounced dead at 7.19pm
A post-mortem examination is expected to be held on Thursday, 3 June.
Police believe they know the identity of the deceased but efforts to inform his next of kin continue.
A total of 10 males – all aged from their teens to early 20s – have been arrested in connection with the incident on suspicion of offences including affray and murder. They all remain in police custody at this time.
A crime scene remains in place in the park.
Detective Chief Inspector Claire Hine is leading the investigation. She said: “We know the park was busy with people enjoying the sunshine on the Bank Holiday when this horrific incident unfolded. We have spoken to a number of people who have told us what they saw, and we remain keen to hear from anyone who has information, video or images that could assist us. A young man has lost his life in violent circumstances and it is imperative that we have a full understanding of the chain of events that has led up to it. Please contact us immediately.”
Detective Superintendent Barry Loader, from the North West Command Unit, said: “Residents can expect to see an enhanced police presence in the area following this incident. Our thoughts of course are with the young man who has lost his life and we are supporting our colleagues as they work to investigate the circumstances around this terrible incident. Please approach our officers if you have information that could assist.”
Any witnesses or those with information, video or images that could assist police are asked to call 101 reference CAD 5436/31 May.