A teenager has been stabbed to death in a playing field in south west London.
Police were called at 4.45pm on Tuesday to reports of a stabbing in Craneford Way, Twickenham.
Police said the 18-year-victim had sustained knife wounds. Officers attended along with London Ambulance Service.
The victim was taken to an outer London hospital where he was pronounced dead at 5.54pm.
Detective Chief Inspector Vicky Tunstall said the incident was witnessed by a large number of people.
“Some of those people are believed to have filmed events as they unfolded; I ask that any videos are not shared via social media to avoid causing the young man’s family any more distress at this already incredibly difficult time for them.
“Instead, please go to the police immediately. A number of people have spoken to us, but we need to hear from anyone who has information that could help.
“We’re working to establish the motive behind this tragic incident and following a number of leads. If you believe you can help us, then please make contact.”
Chief Superintendent Elisabeth Chapple, commander for policing in south-west London, said: “Our thoughts are with the young victim and his family at this awful time. No young person should lose their life in London and we will do all we can to support out colleagues with their investigation.
“Local residents can expect to see an increased police presence in the area. If anyone has any concerns, or information that could help, I encourage them to contact those officers and tell us what they know.”
A crime scene and cordons remain in place and at this early stage there have been no arrests, they said.
Anyone who witnessed this incident or has footage is asked to call police on 101 or Tweet @MetCC quoting 5697/12OCT.
Information can also be provided to Crimestoppers, anonymously, by calling 0800 555 111 or visiting www.crimestoppers-uk.org