Police are stopping at least two people every day from becoming Islamic extremists, the country's most senior counter-terrorism officer has said.
Mark Rowley, Assistant Commissioner of the Metropolitan Police, said his officers were intervening in as many as 70 cases each month where people were showing signs of being radicalised.
He said it was often members of their own community who were alerting the authorities about the change in someone's character, but said nobody could afford to be complacent in the ongoing fight against terror.
Explaining how the police were able to interrupt a person's path towards extremism, Mr Rowley said it was crucial to spot threats early. "We will get information, someone will see something unusual in their town centre where they work, they might be concerned about terrorist reconnaissance and they will report that to us," he said.
"Or they will see someone in their community, maybe a friend, or a neighbour or an acquaintance who they think is becoming more extreme.
"Picking up people as they gravitate towards extremism early on, so we can intervene with social services and other agencies in a preventative way, is really important.
"We are resolving maybe 60 or 70 cases a month, of which about one sixth of those referrals come from the public."
Mr Rowley's comments came after Sir Bernard Hogan-Howe, the Metropolitan Police Commissioner, warned that a terrorist attack on Britain was a case of "when, not if". But Mr Rowley agreed with Sir Bernard's view that Britain had some notable advantages over other countries such as France when it came to preventing terrorist outrages.
He said the fact that the UK is an island with strong borders, combined with tight gun laws, made it more difficult for terrorists to act.
But he added that it was the cooperation between the police and the public that was Britain's "greatest advantage" in keeping the country safe.
Mr Rowley said: "It has often been said that communities defeat terrorism and now that's more important than ever before.
"The true scale of that collaboration is impressive, but rarely explained. The fact is that we see at least 3,639 contributions from the public every day, helping keep us all safe in our collective effort against terrorism."
Members of the public have assisted the police by calling the confidential anti-terrorist hotline an average of 32 times a day and making on average five referrals of extremist material by websites online and two of potential radicalisation.
Mr Rowley added that every day, some 300 people visit the Prevent Tragedies website; 1,750 National Counter Terrorism Security Office sessions - where specialist officers advise how to protect homes and businesses - are recorded; and 1,550 people either take part in anti-terror briefings or watch a Stay Safe film.
"Every call, every referral, every briefing is part of our joint fight against terrorism," he said.
"All of these contributions are critically important to our ability to keep each other safe."