The UK's terror threat level has been raised from 'substantial' to 'severe' - Home Secretary Priti Patel has confirmed.

The move follows an attack in Vienna on Monday, November 2, that left at least three dead.

What does the change in terror threat level mean for the UK?

The change means that an attack on UK soil is now deemed “highly likely”.

It comes after gunmen – believed by Austrian police to have an Islamist motive – killed three and left several wounded on Monday night as they went on a shooting spree armed with an assault rifle, carrying other handguns, and wearing a fake explosive belt.

It came on the eve of Austria entering a month-long coronavirus lockdown – a move that England will follow on Thursday.

What has the Home Secretary said?

Ms Patel tweeted: “The Joint Terrorism Analysis Centre has changed the UK terror threat level from substantial to severe.

“This is a precautionary measure and is not based on any specific threat.

“The public should continue to remain vigilant and report any suspicious activity to the police.”

What are the threat levels - and what do they mean?

Threat levels are designed to give a broad indication of the likelihood of a terrorist attack.

  • LOW means an attack is highly unlikely
  • MODERATE means an attack is possible, but not likely
  • SUBSTANTIAL means an attack is likely
  • SEVERE means an attack is highly likely
  • CRITICAL means an attack is highly likely in the near future

How are threat levels decided?

The threat level for the UK from international terrorism is set by the Joint Terrorism Analysis Centre (JTAC).

MI5 is responsible for setting the threat levels from Irish and other domestic terrorism both in Northern Ireland and in Great Britain.

According to MI5, in reaching a judgement on the appropriate threat level in any given circumstance several factors need to be taken into account.

These include:

  • Available intelligence: It is rare that specific threat information is available and can be relied upon. More often, judgements about the threat will be based on a wide range of information, which is often fragmentary, including the level and nature of current terrorist activity, comparison with events in other countries and previous attacks. Intelligence is only ever likely to reveal part of the picture.
  • Terrorist capability: An examination of what is known about the capabilities of the terrorists in question and the method they may use based on previous attacks or from intelligence. This would also analyse the potential scale of the attack.
  • Terrorist intentions: Using intelligence and publicly available information to examine the overall aims of the terrorists and the ways they may achieve them including what sort of targets they would consider attacking.
  • Timescale: The threat level expresses the likelihood of an attack in the near term. We know from past incidents that some attacks take years to plan, while others are put together more quickly. In the absence of specific intelligence, a judgement will need to be made about how close an attack might be to fruition. Threat levels do not have any set expiry date, but are regularly subject to review in order to ensure that they remain current.