A foreign student who asked an aggressive bus passenger to stop bullying a tearful woman was beaten unconscious and left with permanent brain damage, a court heard.

Niels Nielson, who was studying in Oxford, was bed-ridden for a month after the attack in Cowley and had to be airlifted home to Germany.

He has since had problems talking, feeding himself, has suffered memory loss and extreme bouts of tiredness. He was diagnosed with a lesion on his brain stem.

James Townsend, 23, of Ridgefield Road, Cowley, denies causing Mr Nielson grievous bodily harm with intent.

A jury at Oxford Crown Court heard yesterday that trouble started on the last bus service from Oxford to Blackbird Leys during the early hours of July 27, 1999.

Jonathan Coode, prosecuting, said Mr Nielson, who was then aged 19, was on the Blackbird Flyer bus with three friends after a night out at the Park End Club, Oxford.

He said that Townsend got on the bus and began smashing bottles, swearing and talking aggressively.

Teresia Manneck, a German student who was one of the people with Mr Nielson, told how Townsend began swearing to himself and then sat down behind two girls.

"He stood next to her and called her names. Niels said 'please stop that' in a friendly manner and 'calm down'. The girl was crying."

The prosecution allege that Townsend told the student to shut-up and that he would be followed when he left the bus.

When they got off, Townsend - who was with three friends - headbutted Mr Nielson.

Miss Manneck's group managed to find a police car on a nearby street, flagged it down and explained what had happened. Mr Nielson was then found unconscious in Garsington Road.

Mr Coode said: "They found Mr Nielson in a sorry state."

Townsend was later arrested and denied causing the injuries. He said that he had witnessed the attack but had tried to intervene. The trial continues.