Roper had "borne a grudge" for two years, the court heard

Gary Roper, 18, from Ilford, east London, punched Triston Christmas, 18, causing him to fall and hit his head on a concrete floor.

Mr Christmas, who pinched Roper's girlfriend on a night out, died a week later in January, the Old Bailey heard.

Roper, found guilty of manslaughter, is remanded in custody until 9 September.

'Borne a grudge'

The two youths had been friends at school but had not spoken since the incident involving Mr Roper's girlfriend.

Robin Grey, prosecuting, said: "He seems to have borne a grudge against Triston Christmas.

"He suddenly, for no apparent reason, struck the deceased on the jaw once and certainly there was at least an attempt to hit him again."

Judge Anthony Morris warned Roper he was facing a jail sentence.

The court was told after the guilty verdict that Roper had a history of violent behaviour.

In 2001, he threatened to kill a girl he accused of spreading rumours about him, and later set fire to her hair.

Then in 2002 he attacked another school pupil with a snooker ball in a sock.