Prime Minister Theresa May has warned that "terrorism breeds terrorism" and that extremists are "copying one another."
In a speech hours after Saturday's incident in London Bridge and nearby Borough Market, May vowed to work with "allied democratic governments to reach international agreements that regulate cyberspace" and prevent propaganda from spreading and attacks from being planned online.
She added: "We cannot and must not pretend that things can continue as they are. Things need to change ... There is — to be frank — far too much tolerance of extremism in our country."
"We've been far too tolerant in allowing people to simply opt out of being British, to opt out of our society, and to opt out of our way of life"
NBC News security analyst Duncan Gardham said that while Britain has "always had a problem” with radicalization, "the change in tempo [of attacks] is palpable.”
He blamed both the “copycat” mentality and ISIS’ propaganda push, but also said the number of extremists in the U.K. was increasing.
“When terrorists see one person launch an attack or commit suicide it emboldens them to do the same thing,” Gardham said. “It does seem to give people toying with the idea a sense of bravado to go through with it.”
He added: "The increase in the number of extremists is largely driven by easy access to homegrown preachers and ISIS propaganda on the internet, particularly YouTube. There are very few cases I deal with in which they have not consumed a huge diet of extremist material from mainstream commercial websites."
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While social media plays a role, Maher said the online eco-system is very different from what it was even just a few years ago.
“Companies like Facebook, Twitter, Google, are acting far more proactively to remove this content, to disrupt it and to make sure it disappears in a very rapid way," he said.
Maher had more sympathy for May’s commitment to tackling extremist preaching and ideology within the U.K.
“We've tolerated really radical speech from all kinds of people who fundamentally preach a message of separateness," Maher said. “We've been far too tolerant in allowing people to simply opt out of being British, to opt out of our society, and to opt out of our way of life."
Rowley, the assistant police commissioner, highlighted that Britain's MI5 domestic intelligence agency and police were conducting around 500 active investigations at any given time, typically involving 3,000 subjects of interest.
Additionally, around 20,000 individuals are former subjects of interest. They also remain on the radar of MI5 and its partners.
“Our work necessarily involves making difficult judgments about how to prioritize the resources available to us at a time when the U.K. is facing a severe and high-tempo terrorist threat,” Rowley added.
Before becoming prime minister last summer, May spent six years as Britain's home secretary, meaning she was responsible for law and order, immigration and security in England and Wales.
Corbyn criticized May for cutting police numbers by as many as 20,000 officers while in her previous role.
His concerns were echoed by Sadiq Khan, the mayor of London and a member of Corbyn's Labour Party.
"It's just a fact that over the last seven years, we as a city have lost £600 million ($774 million) from our budgets," he said. "We have had to close police stations, sell police buildings, and we've lost thousands of police staff."
May responded by stating that counter-terrorism budgets had been protected and police had the powers they needed.
The prime minister also insists that the U.K. is a “world leader in developing a strategy for preventing violent extremism," saying its approach has been “highly successful."
He said the British government has grown less willing in recent years to empower organizations such as his Active Change Foundation to confront and engage with individuals on the verge of being radicalized.
Given his background and history, Qadir believes people like him are able to connect and command the respect of those who require intervention.
“These three people should have been referred to people like me,” he said, speaking of the London Bridge attackers.
His group was backed by the government beginning in 2007, before its funding was cut last year.
While at pains to not politicize the recent attacks, Qadir said: “[May] certainly cut policing, she certainly cut a number of other projects. She certainly cut [anti-radicalization] programs that are effective in prisons.”
However, experts concede that it's difficult to stop anyone who decides to use readily available items like knives or vehicles to cause mayhem.
Would-be terrorists can prepare for such attacks over the just course of a few days — often using encrypted apps to communicate — and launch them before the security services are able to identify a plot.
“The reality is that the terrorist threat now, right now, is very severe not just in Britain but across Europe, across the Western world as a whole,” Kings College London's Maher said. “Attacks like this will continue to get through the net. It's not a case of resigning ourselves to it, but it’s a case of saying, 'This will continue to happen — how can we better guard against it, act against it and continue to mitigate the threat that such events pose to our society.'"
Eoghan Macgurie is a freelance journalist contributing to NBC News from London.
Saphora Smith is a London-based reporter for NBC News Digital.
Michele Neubert is a London-based producer for NBC News. She has been awarded four Emmys, an Ed Murrow and Dupont Award for her work in conflict zones, including the Balkans, Afghanistan and Kurdistan.