Members of the public should always remain alert to the danger of terrorism and report any suspicious activity to the police on 999 or the anti-terrorist hotline: 0800 789 321. If your information does not relate to an imminent threat, you can also contact the Security Service via the How You Can Help us page

What are threat levels?

The system of threat levels has been created to keep you informed about the level of threat the UK faces from terrorism at any given time.

This system helps police and other law enforcement agencies decide how to allocate staff. 

The threat level represents the likelihood of an attack in the near future. We know from experience that some attacks take years to plan, while others are put together very quickly.

The threat levels

There are five levels of threat:

• critical - an attack is expected imminently 
• severe - an attack is highly likely
• substantial - an attack is a strong possibility
• moderate - an attack is possible but not likely
• low - an attack is unlikely

Who decides the threat levels?

The Security Service (MI5) (new window) and the Joint Terrorism Analysis Centre (JTAC) (new window) work together to set the UK's threat level.

To do this, they consider information gathered through intelligence in the UK and abroad. They also consider how terrorist organisations have behaved in the past.

In some cases, counter-terrorism officials have to use their best judgement when deciding just how close a terrorist group might be to staging an attack.

Threat levels do not have an expiry date, and can be revised at any time as the information available to security agents changes.

What should you do?

You should always remain alert to the danger of terrorism, look out for suspicious bags on public transport or any other potential signs of terrorist activity you may encounter.

But you should not let the fear of terrorism stop you from going about your day-to-day life as normal. Your risk of being caught up in a terrorist attack is very low.

Find out more about what you can do to.

The threat levels abroad

For information on the threats abroad, travellers or British nationals overseas should consult the Foreign & Commonwealth Office website (new window) for country-specific advice.