Police chief reveals 18 terror plots thwarted within past two years, despite 'dramatic' fall in tip-offs

• Video report by ITV News Correspondent Paul Davies

Eighteen terror plots have been thwarted within the last two years - despite a "dramatic" fall in the amount of public tip-offs, the head of UK counter-terrorism policing has said.

Assistant commissioner Neil Basu said four far-right radical extremist plots and 14 Islamist terror plots were foiled by police and the security services since March 2017.

But - as a new cinema advert was launched - he called on the public to help the authorities as he issued a warning that far-right groups can exploit ongoing Brexit tensions.

How do police want the public to help?

Mr Basu told ITV's Good Morning Britain more than a fifth of calls and emails passed by the public to police helped foil terrorist attacks during the period.

But he issued a warning after it emerged the amount of citizen tip-offs had more than halved in 2018:

Mr Basu said in 2017 and 2018, just over a fifth of the information passed on was “very significant”, meaning it directly led to the identification of a suspect or plot or was a small piece of the jigsaw that helped a plot be disrupted or criminal be prosecuted.

Why have the public tip-offs fallen?

The counter-terror chief said part of the reason behind the fall could be the dominance of Brexit, which “undoubtedly” took up much attention last year, when there was very little terrorist activity compared with 2017.

Mr Basu said he was “incredibly grateful” that 2018 was spared the level of carnage of the previous year, when dozens of people were killed in attacks in London and Manchester.

However, he warned the “worst-case scenario” was public complacency amid a duel threat from the return of radicalised fighters from abroad and the shifting danger of propaganda online fuelling real-life action.

How is the online threat fuelling real-life action?

Mr Basu said: “It’s not so much the volume of threat, but a shift in the threat to the young and the malleable, even the mentally ill who are being affected by what they are seeing, and they are taking that and then using very low-sophistication measures, things that everyone can get access to – a knife or a vehicle – and making an attack.

“And those are the kind of things that worry us most, they are the hardest to see and they are the hardest to stop.

“And that’s why we need communities to stand up and report changes in behaviour that they are seeing within their communities which might actually help us stop these things before they happen.”

He added: “If one in five times someone picks up a phone or emails us is a significant piece of intelligence, that is a major contribution from citizens and we want that to continue.”

Mr Basu was speaking at the launch of a major cinema advert campaign to increase people’s awareness of suspicious activity and encourage them to report it to police.

What does the ad campaign highlight?

The 60-second film shows a series of scenarios, such as a man stockpiling hazardous material and another buying weapons, before rewinding and zooming in on the danger.

An on-screen message reads: “Unfortunately life has no rewind button. If it doesn’t feel right, ACT.”

Asked why the advert was being shown in cinemas, Mr Basu said: “Well, the great thing about cinema is you’re here, you’re trapped in the audience and you’ve got to watch it.”

It will be shown at 120 cinemas across the UK over eight weeks from January 25.

How big is the current anti-terror operation?

A record 700 terror investigations are ongoing, up from around 500 in 2017.

The 18 thwarted terror plots since March 2017 compared with 30 planned attacks that were successfully disrupted in the previous four years.