A 14-year-old boy groomed into becoming a "deeply committed extremist" would have been "pleased" if his plot to murder police officers in Australia had succeeded, a judge said today.
Sentencing the teenager from Blackburn, Lancashire, Mr Justice Saunders said it was "chilling" that someone of his age had been so radicalised that he intended and wished for people to die.
The youth - Britain's youngest terrorist - was detained for life and told he must serve at least five years in custody before he could be considered for release.
One expert concluded the defendant, now aged 15, presently posed a high risk of serious harm to the public including forces and emergency service personnel worldwide, Manchester Crown Court heard.
Over the course of nine days in March this year the teenager took on the role of "organiser and adviser" to an alleged Australian jihadist in a plan to murder police officers by beheading or with a car in Melbourne the following month.
Anzac Day was the chosen date because of "its importance to Australia and its people" when those who have died in conflict are honoured, the court heard.
The judge said: "Thanks to the intervention of the police in this country and in Australia, that attack and the deaths which were intended to follow never happened.
"Had the authorities not intervened, (the defendant) would have continued to play his part hoping and intending that the outcome would be the deaths of a number of people.
"In March 2015 he would have been pleased if that had happened. He would have welcomed the notoriety that he would have achieved."
He continued: "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."
The defendant felt isolated in terms of his education and home life and filled the "vacuum" in his life with religious extremism, the court was told.
He communicated with extremist propagandists, who either worked for Isis or supported their aims, over the internet.
Mr Justice Saunders said the teenager was intelligent but capable of being manipulative.
He said the evidence suggested that he paid "lip service" to engage with the Government's attempts to deradicalise him through the Channel programme.
The youngster was accepted on to the voluntary initiative in February 2014 but by March this year it was felt he had become "disengaged" with the process.
He was then initially arrested on suspicion of making threats to kill after after numerous concerns had been raised of his extremist behaviour at school including references to beheading teachers, the court heard.
Before his arrest he had exchanged more than 3,000 encrypted mobile app messages with 18-year-old Sevdet Besim.
His contact with Besim was instigated by a well-known Isis recruiter and propagandist named Abu Khaled al-Cambodi, himself an Australian, who has promoted the idea of terrorist attacks in his homeland, said the Crown.
Within hours of the pair first making contact not only had the plotters determined that the attack was to take place in Australia but also the idea of an attack upon police officers was taking hold.
The Blackburn teenager was re-arrested on April 2 when "disturbing material" was found on electronic devices seized from his bedroom.
The youth denied he had any intention of engaging in terrorism and said he had not contacted an Australian collaborator, known then only as Ilyas.
On April 15 Besim conducted further internet research on the Anzac Day parade, including in relation to a particular road.
Three days later the police acted and Besim was arrested where he was found to be in possession of a knife, the court heard
Knives and a large Shahada flag were recovered from his home, along with a phone that contained a martyrdom message.
The Blackburn teenager was also arrested again on the same day but declined to answer questions.
In July he pleaded guilty to inciting terrorism overseas.
Besim is awaiting trial in Australia next year.
The defendant was said to have made "considerable progress" at the detention centre where he is held and people dealing with him on a day-to-day basis, together with experts, are "optimistic" that the progression will continue and he will become deradicalised.
However the judge said the balance of expert opinion in the case was that he was still dangerous within the meaning of the Criminal Justice Act.
The bespectacled teenager, wearing grey trousers, a grey shirt and patterned tie, hugged his parents and family members in turn after sentence was passed down before he was led from the courtroom.
In a statement outside court, his family said they were "shocked and devastated" when he was arrested as they were "completely unaware of his activities".
They were "relieved" that no-one was injured as a consequence of his behaviour and now wished to begin "trying to repair the damage".