A 17-year-old boy stabbed an 18-year-old to death in a row over a girl in a park in Twickenham, the Old Bailey has heard.

Hazrat Wali, 18, of Notting Hill, west London, died in hospital after being attacked in Craneford Way Playing Fields, south-west London, on the afternoon of October 12 last year.

Mr Wali was sitting in the park with Mariam Ahmadazai, a female friend, when they were approached by a group of six teenagers – three boys and three girls – one of whom was the 17-year-old defendant.

“One of the girls commented that Mariam and Hazrat, sitting as they were, looked nice together”, Jacob Hallam KC, prosecuting, told the Old Bailey on Friday.

“The defendant said, ‘I thought he was f****** you’. He then began to swear at Hazrat.”

Mr Hallam said that Mr Wali got to his feet and approached the 17-year-old, who was 16 at the time.

The 17-year-old pushed Mr Wali with his chest, telling him to “come at me then”, Mr Hallam said.

The pair then began to push each other, with their hands down by their sides.

Mr Wali then rang Daler Gull, a male friend, asking that he come to help him as he was going to be in a fight.

“He and the defendant were still pushing each other, and (the female friend) heard Hazrat say ‘hit me with that hand if you can’ and she noticed that, in his left hand, the defendant was holding a knife.

“It was black, about 20cm long, with zigzag-shaped indentations on the top of the blade.”

Mr Wali then told Ms Ahmadazai to step away.

“Hazrat and the defendant continued to push against each other, Hazrat repeating, ‘Touch me with that hand if you can’, Mr Hallam said.

“And the defendant saying, ‘Touch me one more time’.”

Mr Wali pushed the 17-year-old away with his left hand, Mr Hallam said.

The 17-year-old then stabbed Mr Wali in the right side with the knife.

The knife went 10cm into Mr Wali’s body, stabbing into his liver, and causing “massive and fatal blood loss”, the prosecutor said.

He added that pathologists analysed the wound, and found that it would have required “at least moderate force”.

“After he had stabbed Hazrat, it appeared to Mariam that the defendant tried to run off, but Hazrat grabbed hold of the defendant’s jacket,” Mr Hallam said.

“He was saying, ‘Why did you stab me?’, and was shouting for help. The defendant, still seeming angry, was shouting ‘Come at me, touch me one more time’.

“Mariam went to separate the two, and Hazrat picked up a fallen branch as the defendant moved off towards a sign.”

Mr Gull then arrived at the scene.

“He heard Hazrat saying, ‘Why did they stab me?’ and went to him,” Mr Hallam said.

“Mariam was also there, and a teacher from a local school came to help give first aid.”

The final stages of the incident were noticed by participants in a nearby rugby match between Richmond School and Hampton School.

One of the schoolboys gave evidence to the police.

“He heard Hazrat shout, ‘Don’t f****** touch me again” and saw him take off his jacket and pick up a stick, and then chase after someone – the defendant – who moved behind a sign and then both of them went off towards the bridge,” Mr Hallam said.

“A short time later the boy who had had the stick came back and fainted.”

Emergency services attended the scene but they were unable to save Mr Wali’s life and he died about an hour later.

Mr Hallam told the court that the 17-year-old, in recorded prison phone calls, said he had acted out of anger.

“Although he speaks of acting in what he claims was self-defence, he says that when he stabbed Hazrat it was ‘just anger’, and stabbing was ‘a way to release your anger’, Mr Hallam said.

The 17-year-old denies one count of murder.