The man, from Blackburn, Lancashire, identified only by the letters RXG, was described as a “deeply committed extremist” who, aged 14, was days away from helping stage a “massacre” at an Anzac Day parade in Australia in April 2015.
Six months later he was sentenced to life at Manchester Crown Court and told he would only be eligible for parole in October 2020 after serving a minimum of five years in custody after admitting inciting terrorism overseas.
He was arrested last month and, now in his early 20s, is back in custody at a jail in the north of England, security sources told the PA news agency.
He was found to be in possession of a smartphone, which broke the terms of his release on licence.
A Probation Service spokesman said: “Protecting the public is our number one priority so when offenders breach the conditions of their release and potentially pose an increased risk we don’t hesitate to return them to custody.”
During RXG's trial in October 2015, a court heard the 14-year-old had exchanged more than 3,000 encrypted messages from his Samsung phone instructing a jihadist in Australia, Sevdet Besim, to launch “martyrdom” attacks during an Anzac Day remembrance parade in Melbourne.
He was recruited online by Islamic State propagandist Abu Khaled al-Cambodi and took on the role of “organiser and adviser”, suggesting to Besim beheading or using a car and machete to murder police officers.
Australian police were alerted to the plot after British officers discovered material on the teenager’s phone.
One expert concluded the defendant posed a high risk of serious harm to the public including forces and emergency service personnel worldwide.
Jailing him, Mr Justice Saunders said the revelation that someone of only 14 was radicalised to the point of wanting to murder was “chilling”.
The court heard the defendant felt isolated in terms of his education and home life, and filled the “vacuum” in his life with religious extremism.
He had paid “lip service” to the Government’s attempts to deradicalise him through the Channel programme and became “disengaged” with the process.
Police found “disturbing material” on electronic devices seized from his bedroom.
An officer from the hi-tech unit of the North West Counter Terrorism Unit (NWCTU) decoded the encrypted messages exchanged and uncovered the plot.
Anzac Day was the chosen for the attack as it is commemorated each year on April 25, to honour Australians and New Zealanders killed in war.
Besim, at the time 18 and from Melbourne, pleaded guilty to a single terror-related charge and was jailed for 10 years at the Victorian supreme court in 2016.
A ban on identifying RXG was issued at the time, because he was aged under 18. The ban would normally expire on his 18th birthday, but in 2019 he successfully won a High Court ruling giving him anonymity for life, as experts concluded that identifying him would “fundamentally undermine” his rehabilitation.
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