THE parents of a teenage boy who died after being struck by a single punch in an unprovoked street attack last night described the three-year sentence given to his killer as "incomprehensible".

Daniel Crowther, 17, was killed by the punch from labourer Thomas Watson, also 17, outside a pizza shop in Stokesley, North Yorkshire, in the early hours of May 14.

Leeds Crown Court heard yesterday that Watson, who had pleaded guilty to manslaughter, had previous convictions for violence and was under the influence of drink and drugs at the time.

Last night Daniel's parents said: "It is incomprehensible that the person responsible for Daniel's manslaughter will be free in a relatively short period of time, while we have to spend the rest of our lives trying to come to terms with Daniel's death.

"When Daniel was violently and tragically taken from us our lives were changed for ever, we miss him greatly and find it unbelievable that he is no longer with us."

They added: "We will never forget him and the pleasure he brought to us during his short but happy life."

In September last year The Northern Echo launched a campaign demanding tougher prison sentences for one-punch killers.

The Price of a Punch campaign calls for a review of sentencing guidelines amid concern at the jail terms given to those who take lives with a single act of violence.

Yesterday, the court heard how the blow from Watson broke Daniel's jaw in two places and ruptured an artery at the base of his brain.

Michael Smith, prosecuting, said Watson told a colleague that day he had been having problems in his relationship and that he was "going out tonight, and if anyone gets in the way, they had better watch out".

Daniel, a popular Stokesley School student who was an only child, had been out with friends drinking at a local pub and had gone to a takeaway.

Mr Smith said he was sitting on a bench outside College Pizzas, when a car pulled up and Daniel spoke to a 17-year-old girl in the front passenger seat, who asked him if he was "looking for a fight", to which Daniel replied "no".

Mr Smith said: "Daniel went over to the car and leant in to talk to the girl for a few minutes, while the defendant got out of the car, saying "well if you want a fight" immediately before swinging a punch at Daniel's face."

Joseph Spencer, mitigating, said Watson was not looking for trouble, and had been trying to protect the girl, who he thought was pregnant.

However she said in her witness statement she had not felt threatened by Daniel.

Mr Spencer said: "Thomas's childhood was not an easy one, but this man had turned a corner.

"He has remorse for his actions and has tried to apologise personally to Daniel's family."

Watson of Woodhouse Road, Guisborough, had his head bowed for most of yesterday's hearing, at times holding it in his hands.

Sentencing him to three years' detention, Mr Justice Butterfield said: "You killed Daniel Crowther, you did it because you were in an aggressive and angry mood that night, it was an unprovoked assault.

"I am not seeking to place a value on the life of Daniel Crowther; that life was priceless.

"His family and friends are devastated by what you have done, and no sentence I could properly impose would assuage those feelings."

Half of his sentence will be served in custody, before he is released on licence.