A TEENAGER who punched an unconscious man in the street 11 times and broke his jaw twice in "extraordinary violence" has been jailed for four years.

Liam Paul Richardson, then 18, knocked the victim out with a single blow and left him lying unmoving for five minutes, Stephanie Hancock, prosecuting, told York Crown Court.

Then he returned and punched him 11 more times, as well as dragging him a short distance and spitting on him in front of bystanders.

Richardson has no previous convictions.

"It is incredibly difficult to understand how a young man of such character could commit such an offence and what we must concede is sickening violence," said his barrister Andrew Petterson.

Richardson, now 19, of Quarry Mount, Scarborough, pleaded guilty to causing grievous bodily harm with intent.

Jailing him for four years, Judge Simon Hickey said: "It is an extraordinary case, extraordinary in the character of yourself having never committed any offence let alone of this extraordinary level of violence."

Ms Hancock said the victim had to have two metal plates inserted into his jaw, which was broken in two places, and had to live on a liquid diet for six weeks. He also had other injuries including a swelling on the back of his head, a thumb injury and painful ribs.

Two witnesses were so appalled and terrified by what they saw in the early hours of September 4, they left the scene and only returned after Richardson had left for the second time.

They called police, who arrested Richardson on his second return to the scene in York Place, central Scarborough, said Ms Hancock.

"The defendant seemed extremely heavily in drink, he was extremely upset and stumbling around," she said.

The two men had not known each other before encountering each other over a pool table in a Scarborough bar the previous evening.

Then they visited other pubs and bars where the victim bought Richardson and his friends drinks.

Mr Petterson said Richardson was a hard-working young man, who had helped his mother after she had major surgery and also suffered from depression and anxiety.

He had immediately admitted what he had done on arrest and was remorseful.