A man has been arrested in connection with the murder of 14-year-old Martin Dinnegan, Scotland Yard has said.
The 20-year-old was arrested by detectives at an address in Islington, north London, and is being held at an east London police station.
He is the second person to be arrested over the murder in north London.
A 15-year-old youth arrested on Wednesday night is still being questioned, police said.
Martin Dinnegan was stabbed to death on Tuesday night in Islington, north London, after he and his friends became involved in an argument with a group of up to 20 youths.
A post-mortem examination gave the cause of death as stab wounds to the chest, police said.
Just hours after Martin was killed, the capital's spate of fatal knife attacks claimed another young victim, when an 18-year-old man was stabbed in a separate incident.
