A 15-year-old British boy who incited a Melbourne man to behead police officers in an Anzac Day terror attack must serve a minimum five years in custody in the hopes he may be deradicalised.
The boy, who cannot be named for legal reasons, was 14 when he exchanged thousands of phone messages with the alleged Melbourne jihadist, urging him to carry out a knife attack on officers in the name of the Islamic State group.
The boy, from Blackburn in Lancashire and believed to be Britain's youngest convicted terrorist, pleaded guilty in July to inciting a terror act.
He was dubbed "the terrorist" by students at his school because of his extremist views.
In Manchester Crown Court on Friday, Justice John Saunders sentenced the boy to life because he concluded he was still dangerous to the public, with a minimum term of five years in a youth detention centre in England's northeast.
Justice Saunders said he concluded the boy had become a "radical extremist", and played a vital part in encouraging his Melbourne contact to carry out the Anzac Day attack and ensuring he did not back out.
The Melbourne man is before the Australian courts after being arrested a week before Anzac Day, when British police discovered messages on the boy's phone that exposed their plotting.
"The revelation in this case that someone of only 14 could have become so radicalised that he was prepared to carry out this role, intending and wishing that people should die, is chilling," Justice Saunders said.
He said extremist IS propagandists had groomed the boy online, then used him to carry out their wishes.
Justice Saunders said the boy appeared to show good progress in the detention centre where he was being held, but he had to conclude on the basis of expert opinion that he was still dangerous to the public and more work was needed to deradicalise him.
He concluded that a sentence of detention for life was justified.
This means the boy will not be released until he is considered to be not dangerous, so protecting the public from harm.
Justice Saunders said the boy was intelligent and he hoped the risk posed by him would have been removed in five years, and he could be released and "realise his considerable potential to society".
After the sentencing, the boy hugged his crying mother and other relatives before being led from the court wearing the same grey shirt and striped tie he had worn the previous day during sentencing submissions.
Outside court, the boy's solicitor, Daniel King, read a statement from the teen's family saying they were "shocked and devastated" when he was arrested, as until that point they were completely unaware of his activities.
"They are, of course, relieved that no one was injured as a consequence of his behaviour."
Mr King said the family now wanted to start the process of trying to "repair the damage".
One female relative of the boy told reporters as she left court: "I think I'm relieved more than anything."
