A 15-year-old has been charged with conspiring to murder a schoolboy who was stabbed to death in the street.
Baptista Adjei, also 15, from North Woolwich, was attacked on Stratford Broadway, east London, on 10 October.
Police have charged another 15-year-old boy with murder, GBH and two counts of possessing an offensive weapon.
The latest suspect will appear at Stratford Youth Court later, Scotland Yard said.
A man stabbed to death at a London Underground station was an Arsenal fan on his way to a match, the BBC has been told.
Tashan Daniel, 20, was killed in an “unprovoked attack” on the platform at Hillingdon station on Tuesday.
He had been heading to the Emirates Stadium to see the Gunners face Nottingham Forest in the third round of the Carabao Cup, a source said.
It is the third murder investigation on the Tube network this year.
No arrests have been made over the attack, which Det Supt Gary Richardson described as “a shocking act of violence”.
He said the British Transport Police (BTP) investigation was in its “early stages”.
“We believe a group of young men were involved in an altercation on the platform before one of the men received a fatal stab wound,” he said.
Police and paramedics were called to the station in west London at 15:57 BST.
An air ambulance was also sent to Hillingdon, but Mr Daniel was pronounced dead at the scene.
Danielle Foster, who was driving past Hillingdon station at the time of the stabbing, said upon “hearing so many sirens, I knew something terrible had happened”.
“Lots of people were being turned away from the station as it had been closed,” she said, adding: “Then the police helicopter began circling the scene.”
Hillingdon station was closed by Transport for London (TfL) while police searched the area.
The station was closed for the rest of Tuesday evening and reopened at 05:45 this morning.
So far in 2019 more than 100 murder investigations have been launched across London by the Metropolitan Police and BTP.
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.
Three people have been arrested on suspicion of attempted murder after a 15-year-old boy was stabbed.
The victim remains in a critical condition in hospital following the attack in Tottenham, north London, on Friday.
He was found with multiple stab wounds on Willan Road, in the Broadwater Farm estate, at around 11:15 BST.
Scotland Yard said three males were detained in connection with the incident on Friday evening.
Officers believe the boy was involved in an altercation shortly before he was stabbed, possibly by a suspect riding a bicycle.
Police would like to speak to members of the public who gave first aid to the victim at the scene.
Det Insp Paul Ridley said: “I am keen to hear from anyone who either witnessed, or has information concerning this attack.
“The victim, not yet 16 years old, sustained multiple stab wounds and is fighting for his life.
“If you know anything about the circumstances surrounding the incident or if you witnessed it, please do come forward.
“I would also appeal to the members of the public who valiantly administered crucial first aid to the victim to come forward to my investigation team.”
Anyone with information is asked to contact police on 101.