Metropolitan Police Chief Constable Sir Mark Rowley said many are lost in their bedrooms "grazing" on an online diet of school shootings, beheadings and terrorist propaganda.
"If you are lost in your bedroom and you're grazing on a diet of American school shooting materials, ISIS beheadings, extreme right-wing propaganda… material that gives you tactics for use of knives and building explosives, it's horrific and that shouldn't be in kids' bedrooms, but it is," he said.
"They are bouncing between videos of school shootings, other gruesome acts - some of it by terrorist groups, some of it nothing at all to do with terrorist groups - and it's the obsession with violence that is driving some young men to do horrific matters.".
Following the 18-year-old's guilty pleas over the mass stabbing, Sir Keir Starmer said he would look at changing the law to recognise the "new and dangerous threat" of lone attackers not driven by one ideology.
"There are thousands of young men online who are obsessing about violence," he said during a live phone-in on Nick Ferrari's Breakfast show.
