What are the UK terror threat levels and how have they changed?

Watch:UK terror threat level increased to 'severe'

The UK’s terrorism threat level has been raised following two attacks in a month.

Police have declared a blast inside a car outside Liverpool Women’s Hospital on Sunday a terrorist attack but said the motive was unclear.

A man blew himself up with a homemade bomb in a taxi shortly before 11am on Remembrance Sunday, while the driver, who managed to escape alive, has been branded a hero.

It came less than a month after Sir David Amess, Conservative MP for Southend West, was killed during a constituency surgery in Leigh-on-Sea in Essex on 15 October.

Ali Harbi Ali, 25, is accused of murdering the MP and has also been charged with preparing acts of terrorism between May 1, 2019 and September 28 this year.

LIVERPOOL, ENGLAND - NOVEMBER 15: Police and forensic officers carry out a fingertip search at Liverpool Women’s hospital on November 15, 2021 in Liverpool, England. A man was killed when the taxi in which he was riding exploded outside Liverpool Women's Hospital just before 11:00 AM yesterday. The driver of the taxi was injured but survived. Detectives from Counter Terrorism Police North West said three men in the Kensington area of the city were arrested under the Terrorism Act.  (Photo by Christopher Furlong/Getty Images)
Police have declared a car explosion outside Liverpool Women’s Hospital as a terror attack. (Getty)

What the different terror threat levels are

There are five levels of threat giving a broad indication of the likelihood of a terror attack.

Low - an attack is highly unlikely.

Moderate - an attack is possible but not likely.

Substantial - an attack is likely.

Severe - an attack is highly likely.

Critical - an attack is highly likely in the near future.

Which level are we on now?

It is now listed as “severe”, which means an attack is “highly likely”.

Speaking to broadcasters, home secretary Priti Patel said: “The Joint Terrorism Analysis Centre, Jtac, are now increasing the United Kingdom’s threat level from substantial to severe.

“And there’s a reason for that, and that reason is because what we saw yesterday is the second incident in a month.”

Member of the Anglo-Iranian community pays tribute to Sir David Amess MP by laying flowers at Parliament Square.. Members of the Anglo-Iranian communities, supporters of the National Council of Resistance of Iran (NCRI) and British Committee for Iranian Freedom (BCFIF), held a memorial service opposite the UK Parliament to pay tribute to Sir David Amess MP by laying flowers. (Photo by Thomas Krych / SOPA Images/Sipa USA)
Conservative MP Sir David Amess was killed during a constituency surgery. (PA)

How they decide to change from one level to another

The Joint Terrorism Analysis Centre and MI5 are responsible for setting the international and domestic threat levels respectively, taking into account available intelligence, terrorist intentions and capability, and potential timescales for attacks.

Timeline of how the levels have changed

Information on the national threat level was first made available on the MI5 and Home Office websites in 2006.

Threat levels for Northern Ireland-related terrorism started appearing in 2010.

The terrorism threat level system was changed in 2019 to take out ideology so there was a single national threat level.

The threat level had been lowered to “substantial” in February, meaning an attack is “likely”, after being raised to severe in November last year.

Watch: Liverpool hospital blast declared terrorist attack by police