The identity of a teenager who plotted to behead police officers at an Anzac Day parade in Australia will remain a secret for the rest of his life.
The boy, from Blackburn, Lancashire, sent encrypted messages instructing an Australian jihadist to launch attacks at the remembrance event in Melbourne.
Now 18, he was jailed for life at Manchester Crown Court in 2015 after admitting inciting terrorism overseas.
The High Court ruled identifying him was likely to cause him "serious harm".
He is believed to be the youngest Briton guilty of a terror offence, and a ban on identifying him made at the time he was sentenced would normally expire on his 18th birthday.
A number of media organisations made representations to the court, arguing that he should be named.
But the judge, Dame Victoria Sharp, granted him lifelong anonymity - a decision only taken in a small number of cases - including those granted to Jon Venables and Robert Thompson, who murdered Liverpool toddler James Bulger, and child killer Mary Bell.
Sitting with Mr Justice Nicklin, she said the case was "an exceptional one".
"We acknowledge that any prohibition on the identification of a defendant in a criminal proceedings is a serious matter and represents a significant interference with the open justice principle," she said.
"Nevertheless, on the evidence before us, in our judgment it is both necessary and proportionate" as identifying him would "fundamentally undermine" his rehabilitation," she added.
"The position is exacerbated by his autism, which manifests itself in his obsessive behaviour.
"This, combined with his need for recognition and status, makes him very vulnerable to exploitation and potential re-radicalisation."
During his trial, the court heard how at the age of 14, the boy adopted an older persona in messages to alleged Australian jihadist Sevdet Besim, 18, instructing him to kill police officers at the remembrance parade.
He sent thousands of messages suggesting Mr Besim get his "first taste of beheading" by attacking "a proper lonely person".
Australian police were alerted to the plot after British officers discovered material on the teenager's phone.