An A* grammar school student has been handed a suspended sentence after posting bomb-making manuals on neo-Nazi forums and downloading indecent images.
Harry Vaughan pleaded guilty to one count of encouragement of terrorism, one count of disseminating a terrorist publication, 12 counts of possessing a document useful for terrorism and two counts of making an indecent photograph of a child.
He was arrested by police in June last year following an investigation into an online forum, called Fascist Forge, described as a "home for the 21st-century fascist".
At the Old Bailey on Monday, he was sentenced to two years' detention suspended for two years.
Police found that the 18-year-old had been boasting about school shootings, sharing explosives manuals and neo-Nazi propaganda online, expressing homophobic views and downloading indecent images of underage boys.
Vaughan's barrister, Naeem Mian QC, told the Old Bailey that a "toxic cocktail of factors" had led him to "disappear down a rabbit hole of the internet" into a "very, very dark place".
Mr Mian said that the "articulate and intelligent" teenager "on the face of it had every advantage afforded", adding that his parents were bewildered when their son was arrested.
"The internet has opened up a very dark world. We cannot be sure what children are doing in their bedrooms," Mr Mian said.
"The question everyone will have in their minds is one that his parents, who are in court, have been asking themselves throughout proceedings: why? And frankly there is no easy answer."
In a pre-sentence report, Vaughan indicated that there were no "significant political", "racist or homophobic" views expressed during his upbringing.
His extremist views, which he now claims to have abandoned, were said to be "driven by internet use".
The teenager began getting into extremism while at Tiffin grammar school in Kingston, southwest London, where he received four A* grades in his A-level exams.
He had attended two lessons on dealing with de-radicalisation in December 2018, one focused on a case study of a neo-Nazi who had changed his ways.
Police found Vaughan's school account and USB stick had been used to download neo-Nazi material.
They also discovered that he had searched for a number of schools near his home on Google Maps.
Several homemade posters were found in his bedroom, including one of the Norwegian killer Anders Breivik and the words "every girl loves a mass murderer" as well as the words "it's okay to be a school shooter" and "it's okay to be a Nazi".
Thousands of files were found on his devices, including footage of the Christchurch massacre, indecent images of children and videos linked to extreme right-wing topics, firearms and bomb-making.
Prosecutor Dan Pawson Pounds said: "The material demonstrated unequivocally that Vaughan had an entrenched extreme right wing and racist mindset, as well as an interest in explosives, firearms and violence more generally."
Commander Richard Smith, from Scotland Yard's Counter-Terrorism Command, made an appeal to the public to help spot the signs of radicalisation.
He said: "Any young person can be radicalised - but they could be helped too.
"If you have any concerns at all, act decisively, talk to the police before it's too late. We have officers who are specially trained and ready to help people who are becoming radicalised choose a better life for themselves."