A 15-year-old boy has been arrested on suspicion of murder following the fatal stabbing of a teenager in Croydon on Thursday evening, the Metropolitan Police said.
The teenager was arrested on Friday afternoon, and is in custody at a south London police station, Scotland Yard said.
Police officers were called to the scene of the stabbing in Ashburton Park, Croydon, shortly after 7pm on Thursday evening and found a 15-year-old boy suffering from stab wounds.
Despite administering first aid to the boy, he was pronounced dead at the scene.
A crime scene remains in place and inquiries continue, the Metropolitan Police said.
The victim’s family have been informed but formal identification has not yet taken place. A post-mortem examination will be held in due course.
The killing of the 15-year-old in Croydon and a 16-year-old in Hillingdon, who died just an hour later at 8.25pm on Thursday evening, became the 29th and 30th deaths in the capital, surpassing a peak of 29 in 2008 - making it the worst year on record for teenage killings in London.
Police remained at the scene overnight on Thursday
Speaking from the scene of the fatal stabbing in Croydon, Metropolitan Police Commander Alex Murray said: "My message today, other than speaking to the families and friends of those that London has lost, is to say you cannot carry knives in London.
"This is what happens when knives are carried and we all have a role in relation to tackling knife crime."
Mayor of London Sadiq Khan said he was devastated following the deaths of two teenagers within an hour of each other on Thursday night.
"The safety of Londoners will always be my number one priority," the mayor said.
"I refuse to accept that the loss of young lives is inevitable and will continue to be relentless in taking the bold action needed to put an end to violence in our city."
No arrests have been made in the Croydon stabbing and police have asked anyone with information to call them via 101 quoting reference CAD 5443/30Dec.