A row over teenagers throwing conkers led to the death of a 21-year-old student in Edmonton, the Old Bailey has heard.

Steven Grisales went over to talk to some youths who had been throwing the conkers still in their spiky husks. But within minutes, Mr Grisales had been stabbed through the heart and died the next day.

A 15-year-old youngster, who cannot be identified for legal reasons, denies murder.

Mr Grisales was walking to Silver Street station on August 31 last year when he was attacked in College Close.

Andrew Edis, QC, prosecuting, said: "This was a sudden, unnecessary killing as a response to a confrontation which took place in the street, which was about nothing very much."

After Mr Grisales collapsed onto the pavement, local residents tried to help him. He was taken to hospital but died despite emergency surgery.

Mr Edis said two of the three youths handed themselves into police a few days later. The accused youth handed in a prepared statement in which he put the blame for the stabbing on the third youth.

Referring to the incident which sparked the death, he said he and his friend were throwing conkers at two girls and the other youth.

"He was aggressive and abusive. He was very angry and the man crossed the road and picked up a skateboard and tried to hit me twice," he said.

"I punched him in the face in self-defence. I saw my friend punch him in the chest."

The trial has been adjourned until Wednesday.