The number of teenagers arrested for terrorist offences in the UK is increasing.
Home Office figures for 2020 show that although more people under 18 were detained than in the previous year, the overall number of people arrested dropped to its lowest level in nine years.
Britain's intelligence services revealed two plots by Islamist extremists and one right-wing terrorist plot were prevented since the beginning of the pandemic, bringing the number of foiled attacks since March 2017 to 28.
Last year, the number of people under 18 arrested for terrorism rose by four percentage points.
The UK's senior national co-ordinator for counter terrorism policing, Deputy Assistant Commissioner Dean Haydon, said a "worrying trend" is developing.
"Unfortunately, we are seeing increasing numbers of young people arrested in relation to terrorism," he said.
"But it doesn't have to be this way. Ideally we would identify when a young person is being led down the path towards terrorism activity and use the Prevent programme to try and put them on a different path.
"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.
"But currently just 2 per cent of people we help through Prevent come to the programme because of concerns raised by those same people who know them best."
On Thursday, UK Foreign Secretary Dominic Raab said that youngsters were radicalised during lockdown.
The UK recorded a 7 per cent increase in 2020 from the previous year in the amount of terrorism-related content viewed online and Mr Raab said the UK is tackling the propaganda "head on".
"Terrorists have digital access to those who are probably the most susceptible to extremist narratives," he said.
“And we can see a worrying rise in the proportion of children and teenagers arrested for terrorism offences.”
He said a major concern was the “perfect storm” of young people stuck indoors during lockdown, and going online to relieve their boredom where they were subjected to extremist indoctrination.
In 2020, there were 185 arrests for terrorist-related activity in Britain. A Home Office report said all arrests were below the average as a result of the pandemic.
"The reductions may reflect the general reduction in crime during this period when there were public health restrictions in place to control the spread of the Covid-19 virus," the report said of terrorism-related arrests.
"This effect was most marked in April to June 2020 during the national lockdowns in England and Wales with just 31 arrests in that quarter.
"As restrictions were eased over the summer months, the number of arrests increased, for example, up to 53 arrests in the latest quarter."
Ninety per cent of those arrested were male.
Mr Haydon said that terrorists continued to plan attacks.
“These statistics tell me two things. Firstly, that despite facing unprecedented challenges brought about by the pandemic, counter-terrorism policing continued to keep the public safe by making 185 arrests across more than 800 live investigations – stopping three possible terror attacks in the process," he said.
“Secondly, that while the rest of us have been focused on protecting ourselves and our families from this terrible disease [coronavirus], terrorists have not stopped planning attacks or radicalising vulnerable people online.
“As we follow the government’s road map out of the tightest restrictions, there will be greater opportunity for terrorists to operate and we want the public to join the police, security staff and retail workers in a collective community effort to minimise the chance of attack.
“When we say that ‘communities defeat terrorism’, it is not just a catchphrase. We know from experience that public information and action help save lives and lead to the significant arrests detailed in these statistics."
Last year, 54 people were tried for terrorism offences and 49 convicted.
There are 209 people in UK prisons for terrorism offences, 75 per cent of whom were categorised as holding extreme Islamist views.
Mr Raab said the rise of violent internet indoctrination is at a “critical moment” and that the security services were fighting hard to combat the threat.
He said that ISIS was "still able to carry out lethal attacks" and it remained the UK's "most significant terrorist threat".