A teenage thug knocked a man unconscious and then dropped his tracksuit bottoms and pants and sat on his face, a court heard.

Sentencing Lewis Bond to 18 months youth custody, a judge, who was shown CCTV film of the attack, said it was "a very unpleasant act of gratuitous degradation" after causing serious injury.

Victim Thomas Arnold fell awkwardly when floored by the punch and suffered fractures to his left leg.

Bond, of Homewood Avenue, Sittingbourne, admitted inflicting grievous bodily harm.

Maidstone Crown Court heard Mr Arnold and his girlfriend Lisa Stansil had been to a snooker club in Sittingbourne High Street on October 20 last year.

As they walked past a nearby Wetherspoons pub in the early hours they stopped to talk to people outside.

At first, it was friendly, but then Miss Stansil and another girl started arguing and fighting.

Prosecutor Martin Yale said Mr Arnold stepped in as a peacemaker and tried to separate them.

"This has been a wake-up call. He has addressed for the first time his problem in managing alcohol" - Sarah Haroon, defending

"While this was going on the defendant threw a punch at Mr Arnold’s head," said Mr Yale. "The force of the blow was so hard that Mr Arnold was knocked unconscious.

"He fell to the ground. His leg gave way. There were two breaks to the leg. While unconscious on the floor with a broken leg the defendant took down his trousers and underwear and rubbed his bottom in Mr Arnold’s face.

"Miss Stansil went over to him and lay on top of him to prevent him from being attacked any further."

Bond, 19, and his girlfriend walked off. An ambulance was called and Mr Arnold was taken to Medway Hospital. He had two operations and was transferred to the Queen Victoria Hospital in East Grinstead for further surgery.

When arrested, Bond, who has 12 GCSEs, claimed he punched the victim because he was being aggressive and making threats.

"After he fell to the floor I put my bum on his face," he said. "I pulled down my trousers and sat on his face."

Asked why he did it, he replied: "He was being so macho and I thought he was a complete idiot."

He added when he sat on Mr Arnold’s face he moved around because he thought it was funny.

"He said he now thought it was childish," said Mr Yale. "He said: ‘It was pretty dirty really.’"

Bond was given a community order in March 2011 for two offences of grievous bodily harm at an 18th birthday party at Highstead School in the town.

Judge Charles Macdonald QC said the victim had been doing nothing but trying to make peace between the two women.

“This is a truly overwhelming case because clearly the incident is shown on CCTV, including the act of degradation,” he told Bond.

“After the man fell to the ground unconscious you lowered your track trousers and underpants and sat on his face, moving back and forth in a plainly insulting and offensive manner.

“The severity of the leg injury was not foreseen by you but this can only be dealt with by means of immediate custody.”

Sara Haroon, defending, said Bond acknowledged his disgraceful behaviour and was remorseful. The single blow was followed by “a juvenile prank”.

“This has been a wake-up call,” said Miss Haroon. “He has addressed for the first time his problem in managing alcohol. It will be his first taste of custody.”