The identity of Britain's youngest terrorist, who plotted to murder police officers in Australia, will remain a secret for the rest of his life following a High Court ruling.
The teenager, from Blackburn, Lancashire, who can be identified only as RXG, sent encrypted messages instructing an Australian jihadist to launch attacks during a 2015 Anzac Day parade.
Now 18, he was jailed for life at Manchester Crown Court in October 2015 after he admitted inciting terrorism overseas.
A ban on identifying him made at the time he was sentenced would normally expire upon his 18th birthday.
But, in a ruling delivered on Monday, Dame Victoria Sharp granted him lifelong anonymity.
The judge said that identifying him was likely to cause him "serious harm" and it was therefore necessary for the rare step - taken in only a small number of cases.
Sitting with Mr Justice Nicklin, she said: "We are satisfied that RXG's case is 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 added.
"Nevertheless, on the evidence before us, in our judgment it is both necessary and proportionate."
The judge said experts had concluded that identifying RXG 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."
At the age of just 14, the teenager took on the role of "organiser and adviser" and suggested beheading or using a car to kill officers.
He was recruited online by Islamic State propagandist Abu Khaled al-Cambodi.
Over nine days in 2015, he sent thousands of messages to 18-year-old Sevdet Besim, instructing him to kill police officers at the remembrance parade in Melbourne.
Australian police were alerted to the plot after British officers discovered material on the teenager's phone.
Anzac Day is held on April 25 each year to commemorate Australians and New Zealanders killed in conflict and, in 2015, marked the centenary of the First World War battle in Gallipoli.
The youth's lawyers argued at a hearing in November last year that there was a "significant risk of attacks or retaliation against him" if his identity was made public.
They also said he would be at risk of "re-radicalisation" by extremists and that his relatives would be likely to face reprisals were he named.
A number of media organisations made representations to the court, arguing that he should be named.
Only a handful of lifelong anonymity orders have been made, including those granted to Jon Venables and Robert Thompson, who murdered Liverpool toddler James Bulger, and child killer Mary Bell.