A peace activist has been jailed for eight months after an attack on a young rock singer which left him in a coma.
Billy Leeson was left in a coma by the attack
New Zealander Christiaan Briggs, 30, punched Les Incompetents frontman Billy Leeson, 19, after a dispute on a bus in Islington, north London, in June.
He was left critically ill and in a coma after hitting his head, but has since left hospital, a court heard.
Briggs, who once acted as a human shield in Iraq, admitted a charge of grievous bodily harm.
Leeson was knocked unconscious by the assault and needed to be resuscitated, Snaresbrook Crown Court was told.
Part of the front of his skull was removed to relieve pressure on his brain. A tracheotomy to ease breathing was also carried out.
He was in hospital for six weeks and had to learn how to walk again.
Briggs, of Kingsbury, north-west London, pleaded guilty to causing grievous bodily harm at a hearing in June.
He spent three weeks in Iraq with the Truth Justice Peace Human Shield Action Group in 2003 in protest at the US-led invasion.
Judge Peter Birts QC told Briggs, an architectural technician and former Green Party candidate, he had expressed "genuine remorse" but that a prison sentence was inevitable.
He said Briggs had injured "someone who was so talented and gave pleasure to so many others in life".
The court heard Mr Leeson had been on a bus with his girlfriend when she complained Briggs was staring at her.
Prosecutor Busola Johnson said the singer asked him to "look elsewhere" and after a further "exchange of words", got off in Camden.
She said Briggs promptly followed and as Mr Leeson walked off, punched him "without warning" on his left cheek.
Bartholomew Cosella, defending, insisted Briggs was a "committed pacifist" who had devoted himself to "trying to make the world a better place".
Det Sup Sean Smyth said Mr Leeson "is pleased with the outcome of this case".
"He continues to recover from his injuries," he said.