The boy, now 16, was found guilty of attempted murder last week after he stabbed a 15-year-old girl at Thorpe St Andrew School on March 11.

His father, speaking to the BBC and referred to as John, said he believed his son was "radicalised" by extreme content online and apologised to the victim and her family.

Police and emergency services at Thorpe St Andrew High School (Image: PA)

Neither John's son or the victim can be identified for legal reasons.

"We're so very sorry for what happened," John said.

He said he did not want to "absolve" his son of responsibility, but believed exposure to violent and hateful content online played a significant role.

During a two-week trial at King’s Lynn Crown Court, it was revealed the boy had a fixation on serial killers and mass shootings, harboured deep-seated misogynistic views and had planned to target others in the attack.

He dressed in black, wore a face mask and used a kitchen knife to carry out the stabbing.

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