"I've wetted your boy," Leighton Amies shouted at a group of youths after stabbing 14-year-old Tomasz Oleszak in the chest at a nature park in Gateshead last October.

That statement was made "triumphantly", Mr Justice Martin Spencer said during sentencing at Newcastle Crown Court.

Amies had "relished" having a knife that night, which he had taken from his kitchen at home, the judge added.

Amies, also 14 at the time, was convicted of murdering Tomasz last month.

It has now been revealed that he was excluded from his primary school for threatening to stab a teacher, and from secondary school for arson when he set fire to a plastic window.

Images found by police after his arrest showed he had an interest in knives.

Speaking of Tomasz, the judge told the teenage defendant: "This was the beautiful, exceptional, gifted boy whose life you, Leighton, brought to an end."

While accepting that Amies did not instigate the incident, he said Tomasz was blameless, and the group that followed Amies must live with the knowledge that their "stupidity" led to his death.

Amies also slashed another group member's coat and was convicted of attempting to cause grievous bodily harm, for which he was sentenced to 13 months, which will be served concurrently.

He had previously admitted carrying a blade.

Since being held in secure accommodation he has made educational progress, the judge said, and his reading age has increased from 10 to more than 13 years old.

He told Amies: "You took the knife to the scene, intending to have it available to use as a weapon, which you then did.

"Once you have served the minimum term, less the time spent on remand, you will then be eligible for early release but you will remain on licence for the rest of your life and may be recalled to custody at any time."

Amies was walking through Whitehills Nature Park with his girlfriend at about 8pm last October when a group of youths followed them.

He was carrying a serrated kitchen knife in his jacket pocket for "reassurance", he said.

After he was found guilty, Mr Justice Spencer lifted a ban on the media identifying him, to deter other teenagers from carrying knives.

Peter Makepeace KC, defending, told jurors that Amies had not been looking for trouble.

"This is a 14-year-old under group attack and having to make terrible decisions under a moment's notice," he said.

Tomasz's mother, Kamila Wisniewska, paid tribute to her "kind, loving and sporty" older son, who was born in Poland and moved with his family to Gateshead in 2012.

She said he was popular, respectful and hated violence.

Ms Wisniewska was called to the scene of the stabbing. "I have flashbacks to that night, trying desperately to keep my boy alive," she said.

Speaking outside court, Detective Inspector Chris Deavin said: "This is a truly tragic case and our thoughts very much remain with Tomasz's heartbroken family and loved ones, who are facing the worst sentence of all - a life without Tomasz.

"This case should send an unequivocal message to anyone who chooses to carry a weapon of any kind or believes that violence is acceptable that the consequences can be devastating.

"Look at the pain this tragedy has caused - not only could you take away someone else's future and destroy the lives of their loved ones, but also ruin your own life and those of your family and friends."