A fourth teenager has been arrested on suspicion of the murder of a boy at a chicken shop in central London.
Josiph Beker, 17, was stabbed to death outside Edgware Road KFC, Westminster, at about 14:00 BST on 10 September.
A 16-year-old boy was arrested on Sunday in connection with the murder. He remains in custody.
Two 16-year-old boys were charged with murder on Saturday. An 18-year-old arrested over the murder has been bailed pending further inquiries.
More than 350 people were arrested across both days of the Notting Hill Carnival, the Met Police has said.
A Section 60 order, giving police additional stop and search powers, was enforced on Monday after reports of “incidents of violence”.
Thirty officers suffered minor injuries at the event, with 37 people held for assaults on police.
Cdr Dave Musker said he was “happy” with how Carnival went but “extremely disappointed” by the attacks.
“Officers put themselves on the frontline and should, under no circumstance be assaulted for protecting the public,” Cdr Musker, who was the Met’s lead officer for the event, said.
By 22:00 BST on Monday, 353 arrests had been made with 111 on Sunday and 242 on the second day of the event.
The majority – some 162 – were for drugs, while 34 were for possession of offensive weapons, 31 for public order offences and 10 for sexual attacks.
An additional 30 arrests related to the event were made by British Transport Police on London’s transport network.
A Section 60 order had been authorised for specific stations, lines, and trains on Monday “to protect the travelling public and prevent serious violence”, the force said.
More than one million people attended the festivities as record temperatures were recorded in west London.
A man has been arrested after climbing over Buckingham Palace’s front gates in the middle of the night, police have said.
The 22-year-old was held on suspicion of trespass at around 02:00 BST on Wednesday by specialist royal officers, the Metropolitan Police Service said.
The Queen was in residence at the time, a palace spokeswoman confirmed.
The intruder was not carrying a weapon and the incident is not being treated as terror-related, the force said.
The palace spokeswoman declined to say whether the Queen had been informed of the incident.
At their lowest point the gates are several metres high.
The man has been released under investigation, Scotland Yard said.