A 15-year-old youth is facing a life sentence after being found guilty of stabbing a student to death in a row over conkers.
The youth was found guilty at the Old Bailey of murdering architecture student Steven Grisales, 21.
Mr Grisales died last August after he went over to remonstrate with youths throwing conkers still in their spiky husks.
He was walking to Silver Street station, Edmonton, north London, when he was attacked in College Close.
The youth, who cannot be identified for legal reasons, was remanded in custody to be sentenced next month.
After the verdict, Detective Inspector Richard Beadle said: "Steven did no more than stand up to unruly youths and for that he has lost his life.
"But for the courageous intervention of a local resident, I am convinced the attack would have continued.
"He placed himself in front of Steven whilst the youth continued to try to stab him. The defendant's arrogance and contempt for others belies his age."
Steven's mother Jasmid said in a statement: "Steven was always loved by every person who had the privilege of knowing him."
The accused blamed another youth for the stabbing, but was identified from his distinctive clothing on CCTV. He claimed Mr Grisales had over-reacted and tried to hit him with a skateboard.