MI5’s chief has revealed that the agency had found itself investigating a neo-Nazi terror suspect who was 13 years old, part of a “rising trend” of radicalised teenagers becoming engaged in rightwing terrorism across the UK. Ken McCallum, the domestic spy agency’s director general, warned that extreme rightwing terror accounted for one in five of all counter-terror investigations, a threat that had “grown and morphed quite substantially over the last five to 10 years”. A particular problem, he said, was the “high prevalence” of teenagers in rightwing terror investigations, which he suggested was because youngsters were being swept up in a “toxic ideology” of “online extremists and echo chambers”. The youngest person who featured in MI5’s investigations was 13 years old, McCallum said, and had “stimulated quite a bit of risk in a number of places” – largely online – before investigators realised how young he was. McCallum did not name the youngster, but it is understood that the person he was referring to is a teenager from Cornwall who was convicted in February at the Old Bailey after pleading guilty at the age of 16 to 12 terror offences. The youngster had downloaded his first bomb-making manual aged 13. Working from his grandmother’s house he had become the British leader of banned neo-Nazi group, the Feuerkrieg division, a group that wanted to enact “white jihad”. The boy, who cannot be named for legal reasons, was sentenced to a two-year youth rehabilitation order. At the end of the trial, the presiding judge said that the teenager had “significant vulnerabilities” and that a jail sentence would undo progress he had made since he was arrested in July 2019. McCallum said he recognised that the presence of teenagers in terror investigations was a complex matter. “Clearly, in all such cases there is an important child protection angle that has to be factored in also,” he said. But the spy chief stressed that the trend was marked: “It is already the case that in quite a range of our investigations we do sadly see teenagers, minors, under the age of 18, some under the age of 16, presenting sharp risk.” Asked why teenagers might be drawn to this ideology, he suggested that in some cases, it may be a “piece of rebellion as teenagers find their way in the world”, and he described the threat as an almost “cult-like phenomenon”. Some teenagers were inspired or rallied by other figures who had committed extreme rightwing atrocities around the world, in places such as Christchurch in New Zealand, McCallum added, although he declined to cite any of the figures by name. MI5 took over the lead responsibility for countering extreme rightwing terrorism from the police from 2018. The spy chief said that, of 29 late-stage attack plots that had been disrupted over the last four years, 10 had been from the extreme right. One serious case McCallum highlighted was the recent conviction of neo-Nazi Dean Morrice, a former Ukip member who posted violent racist, antisemitic and Islamophobic propaganda online and had collected the means for making an improvised bomb at home. He was jailed last month for 18 years. But McCallum said it was unclear if the extreme rightwing threat was growing, or whether in fact MI5 was finding more extreme rightwing activity now that it was actively looking for it. It was, he said, “genuinely quite difficult to know right now” if it was “still spiralling in absolute terms” or more on a “plateau”. Earlier this week an American neo-Nazi group called the Base, which is led from Russia, was banned by the Home Office. The group had been actively trying to recruit in the UK and is the fifth far-right group to have been banned under anti-terror laws. The MI5 chief also warned that Islamist terrorists “will seek to take advantage of opportunities” to rebuild as US, UK and Nato forces exit Afghanistan. It could be the case “some terrorist groups might seek, for example, to reestablish training facilities” – along the lines of al-Qaida if “pockets of ungoverned space open up”. Other groups, with no position on the ground in Afghanistan, may also seek to gain “propaganda opportunities” online if the Taliban were to gain significant ground following the withdrawal, although McCallum cautioned that the overall situation in the country was difficult to predict.