A record number of children were arrested on suspicion of terror offences in Great Britain in the last year, a development that investigators have linked to the shutdown of schools during the early stages of the pandemic. Figures released by the Home Office show there were 25 such arrests of under-18s in the 12 months to September, the majority in relation to far-right ideology. This was an increase from 17 arrests the previous year. Under-18s accounted for 13% of all terror arrests last year, up from 8%. “We are very concerned that children are becoming an increasing proportion of our arrests,” said the deputy assistant commissioner Dean Haydon, the senior national coordinator for counter-terrorism policing. In February a 13-year-old neo-Nazi from Cornwall was found guilty of possessing bomb-making manuals and disseminating far-right materials online. Last week a 17-year-old from Derbyshire appeared before Westminster magistrates charged with possessing and sharing a terrorist publication. A trial is expected next year. Investigators highlighted the impact of pandemic-related school closures, arguing that educational settings help normalise behaviour, while schools regularly report cases of concern to Prevent, the government’s deradicalisation programme. Loneliness during lockdowns and the ease with which young people with time on their hands can seek out extremist material online when not being supervised are also factors driving the rise in numbers, police believe. Some extremists are using Covid conspiracy theories and online gaming channels as a means of recruitment. At the same time, restrictions on socialising and movement helped push down the number of adult terrorism arrests by 13%, reflecting wider lockdown-related falls in crime. Officers said they wanted parents to be more aware of the risks and to be prepared to call in Prevent, which few currently do. “Our research tells us that parents, family members and friends are the first to see the changes in behaviour which might indicate that a loved one is being radicalised,” Haydon said. “But currently just 3% of people we help through Prevent come to the programme because of concerns raised by those same people who know them best.” He advised parents to seek advice from the Act Early scheme. Counter-terrorism police said they had stopped 32 “late-stage” plots in the four years from 2017, an increase of one since September and four since March. Those uncovered by police and MI5 since March include three far-right plots and one leftwing, anarchist or single-issue plot – while the total of Islamist plots has remained unchanged at 18. There have been two terror attacks this autumn. In October the Conservative MP Sir David Amess was stabbed to death at his constituency surgery in Leigh-on-sea, Essex, in what is believed to have been an Islamist attack. A month later a man blew himself up in a taxi outside Liverpool women’s hospital for reasons investigators are yet to firmly identify. Reflecting the increasing focus on far-right activity, the number of white people arrested as terror suspects is now double the number of arrests of people from an Asian background. The Home Office data said 101 white people were apprehended, up 5%, and 49 people of Asian ethnic appearance, down 40%. Last month figures from Prevent covering 2020-21 showed that 310 people were referred to the programme by schools, colleges and universities because of far-right links, and 157 were referred because of vulnerability to Islamic extremism.