Information from the British public has helped thwart a string of terror attacks, Britain’s most senior counter-terrorism officer has revealed.
Assistant commissioner Mark Rowley told the Press Association that security services have prevented 13 potential terrorist attacks on the UK in less than four years.
In a third of the most high-risk investigations, officers were helped by public information.
That figure is one higher than the last tally given in October.
More than 500 live investigations into potential terrorist plots are being run at any one time in the UK, he also revealed.
Rowley disclosed the figures as he launched a major appeal for the public to report any suspicions and act on their instincts, saying their help is critical to foiling atrocities.
Describing the contribution as “extraordinary”, Rowley said: “Some of that information is a change in someone’s behaviour, some of that’s about suspicious activity.
“Sometimes that public information has actually started an investigation. Other times it’s part way through and it corroborates some things or adds to things we already know.
“The public are making a great contribution which is critical to us all working together to protect ourselves from terrorism.”
Despite foiling a string of plots since the murder of Lee Rigby in May 2013, the senior officer stressed that the threat continues to be severe while authorities have some big operational challenges.
Investigators have been making arrests at a rate of close to one a day on average since 2014.
The official threat level for international terrorism has stood at severe - meaning an attack is “highly likely” - for more than two years.
Rowley said that “tempo” of activity continues. He identified a host of challenges including encrypted communication methods, propaganda and the range of possible attack methods.
“Now we worry about everything from fairly simple attacks with knives or using vehicles all the way through to the more complex firearms attacks,” he said.
“All of that means that our job remains difficult. We’ve got over 500 investigations at any one stage.”
In that context, the flow of information from the public to build intelligence on individuals or groups plotting attacks is seen as more important than ever.
In the year to March, the anti-terrorist hotline received more than twice the number of calls on the previous 12 months, with 22,000 people making contact.
Rowley said: “Even though the public are doing a great job, we want more help.”
A poll of more than 2,000 adults found that most respondents believed it was important for communities to work with police to defeat terrorism.
However, a quarter of those surveyed said they might not report their suspicions because of fears over wasting police time and almost two in five were unsure about what suspicious behaviour might look like.
As part of the Action Counters Terrorism campaign, a podcast has been produced revealing previously untold stories of how terrorist attacks on UK soil were prevented, featuring accounts from detectives, bomb disposal and surveillance officers.
Rowley said the aim of releasing new material was to give an insight into how terrorists might prepare and provide more confidence for the public to report any suspicions.
He said: “I think what often happens is a member of the public will see something, or hear something, and think ‘well that’s a bit odd, but maybe I’m overreacting and I won’t bother telling anybody’.
“Us putting more information out there, the aim is that it gives that bit more confidence for the public.
“We will respond carefully, we won’t overreact.
“If it turns out to be a call where you made it with good intent but actually there was no problem at the end of it, that’s fine.
“We’d rather have many calls like that, rather than miss out on the critical one that helps us stop an attack.”
Security minister Ben Wallace welcomed the campaign, saying: “The horror of recent terrorist attacks in Europe and beyond is a shocking reminder of the threat we all face.”