Emergency plans to cope with a terror attack in the UK have been changed in the wake of the Paris shootings because it was "not everything we anticipated", the country's chief anti-terror officer said.
Scotland Yard assistant commissioner Mark Rowley, the national policing lead for counter-terrorism, said the Islamic State (IS) is unlike any other threat Britain has faced before in its bid to recruit and corrupt people.
He shared Prince Charles' fears of how young people in the UK are being radicalised in their own communities, warning "it's what worries us most of all". Words: PA
Around 600 people are believed to have travelled to Syria and Iraq from the UK since the conflict began and around half have returned home.
Asked about the anti-terror unit's reaction to the Paris attacks, Mr Rowley told BBC One's Andrew Marr show: "In terms of our national firearms capability, we've asked is it strong enough? How's it placed? How's it organised?
"We've arranged to be able to deal with those sorts of events and we have some well-tested exercises and command and control regimes for working across the country on counter-terrorism.
"But you look at an event like Paris and you think not everything in that we anticipated, so we're going to have to make some refinements to our plans to improve."
He added that IS is not a "classic terrorist organisation" but a "very different" threat.
"We're dealing with a group whose trying to create a corrupt cult of people, followers who will act in their name," he said.
"They're trying to attract misfits, criminals and the vulnerable."
Asked about Prince Charles's fears about the "alarming" extent to which young people are being radicalised, he added: "That's the dynamic that worries us most of us all, is the ability of IS to reach in to communities.
"We've been making lots of appeals to communities over the past year asking them for increasing amounts of help and we've seen that, we've seen more information coming forward."
The police have recently strengthened their cyber resources, leading to 1,000 "unsavoury" posts a week being taken down.
However, Mr Rowley said more money is needed to grow the anti-terror unit over the next year and discussions with the Government for funding are ongoing.
Last month chief constables across the country began reviewing how to strengthen the protection of their officers and the Jewish community in the light of the Paris terrorist attacks.
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