A 16-year-old boy has been jailed for seven years for his part in a "disgraceful and brutal" gang attack which left a boy in a coma for two weeks.

William Hutson, of Mitcham Road, Croydon was told he had committed the “most serious form of grievous bodily harm one can imagine”

He was found guilty in January of causing grievous bodily harm with intent and theft in Blagdon Park, New Malden, during the attack in April 2009. He was found not guilty of attempted murder.

Joined by his father in the dock for support, Hutson groaned and muttered upon hearing the sentence, which was delivered by Judge Christopher Moss QC.

Judge Moss reprimanded the teenager for “callously leaving the scene” after leaving the victim for dead following “a disgraceful and brutal attack”.

The father of the 16-year-old victim’s family, who cannot be named for legal reasons, admitted the sentence was harsher than he expected.

He said: "I expected him to get four years but to be honest this still doesn't change anything."

Detective Inspector Brian Fitzpatrick, who led a massive investigation by Kingston police into the crime, admitted resources were stretched due to the sheer size of the operation.

He said: "At one point we were thought it was going to be a murder investigation because the victim was in such a bad way.

“In a way this result is even more satisfying because we did it with limited resources, unlike for murder investigations where they send in the cavalry.”

Hutson was part of a teenage street gang called MG4646 (Murder Gang 4646), comprising around 20 black and mixed race male youths from across south London. Each member had their own nickname, with Hutson known as “H Dot” or “Rizla”.

During the 13-day trial the court was told how the gang came to the park to steal mobile phones and cigarettes from a group of 15-year-olds sitting on a mound.

The incident quickly turned nasty and several members of the younger group were badly assaulted, one girl being punched in the face and a boy being “fly-kicked” to the back of his head, the court was told.

One witness to the attack said he saw a victim surrounded by five gang members.

After being floored by his attackers, the witness saw the boy being rolled down the hill, where he was then repeatedly stamped on and kicked.

He said: “I saw one boy lying there. I thought he was dead.”