Fourth arrest over cyclist Alan Cartwright's murder
A fourth person has been arrested on suspicion of murdering a teenage boy while he was cycling.
Alan Cartwright, 15, was stabbed to death on Friday evening in Islington. His family said the killing was "senseless".
An 18-year-old man was arrested at 06:15 GMT on Thursday after going to a north London police station.
Three young men, aged 17, 18 and 21, were also arrested on Wednesday on suspicion of murder.
The 17-year-old has been bailed until mid-April but the other two remain in custody.
Alan was cycling on Caledonian Road with two friends when they were attacked by three young men, CCTV footage shows.
'I feel numb'
After cycling away, Alan collapsed and was pronounced dead at the scene.
A post-mortem examination confirmed he died from a single stab wound to the chest.
Alan's mother, Michelle Watson, said she "feels angry".
"I want somebody found for this. I just feel numb," the 39-year-old said.
Police are appealing for any information about the murder and the whereabouts of his two friends' bicycles, which were stolen by the suspects.