A teenager who has a left a man seriously brain damaged following a drunken town centre assault has been jailed for about three-and-a-half years.

Jordan Taylor was on a suspended sentence for another 'cowardly' attack when he knocked his victim to the ground on Bridge Street in the early hours of the morning.

And when Malkit Grewal was lying unconscious outside the British Heart Foundation shop the 19-year-old took another swipe and stamped on him.

As a result the 27-year-old victim was rushed to the John Radcliffe Hospital in Oxford where a piece of his skull had to be removed to relieve the pressure.

Now a judge has been told that medics are not prepared to give a full prognosis and they fear he may be severely brain damaged for life.

Colin Meeke, prosecuting, said Mr Grewal had gone out with his brother and mates to celebrate his birthday and had been drinking heavily.

At about 2,30am he was outside in the street making a nuisance of himself, shouting abuse at passers by.

"CCTV shows that Mr Grewal was jumping around the street frankly, it has to be said, looking for trouble," Mr Meeke said.

After exchanging drunken punches with two of the men in Taylor's group the defendant ran up and landed the heavy blow, causing his head to hit the pavement.

"He knocks him to the ground with a single punch, then goes to stamp on his chest. The defence say it was a relatively light stamp," Mr Meeke said.

"The video ends with the defendant and his friends giving each other what they call high fives."

While independent witnesses spoke of how the victim was behaving he said the defendant approached him and landed the punch, followed by a half-hearted stamp.

He said doctors were not prepared to give a full prognosis saying he needs at least a further six months of intensive treatment and rehabilitation.

An earlier hearing was told that he is a professional boxer and was injured in a bout in Japan against Chris Eubank Jr.

Taylor, of Austen Crescent, Liden, pleaded guilty to grievous bodily harm with intent.

The court heard he was put on a six month suspended sentence in Bristol last June after admitting actual bodily harm.

That was a late night attack outside a kebab shop where he punched a man to the head from the side in what the judge called a 'cowardly' attack.

Emma Handslip, defending, said her client was very sorry for what he had done and realised he was facing a lengthy jail term.

She said he could empathise with the victim as his stepfather is in a similar condition in hospital following a car crash.

Passing sentence Judge Robert Pawson said: "However much provocation there was that night there is absolutely no justification for what you did.

"It doesn't excuse what you did and the consequences will be felt for many months, if not years, by Mr Grewal's family and you have that on your conscience."

DC Mike Armishaw from Wiltshire Police said: "It is true to say that the victim was making a nuisance of himself before he was assaulted but that does not warrant the violence that Taylor responded with.

"The victim was knocked unconscious and then kicked when he was on the ground causing very serious brain injuries, the impact of which may have a lifelong detrimental effect for both himself and his family.

"This case shows the very real risk of serious and far reaching consequences even from just one punch."