Home Secretary Priti Patel has confirmed the escalation of the UK terror threat level from "substantial" to "severe" following an attack in Vienna that left at least three dead. The change means that an attack on UK soil is now deemed "highly likely". 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 potential is for UK based 'lone wolfs' to be emboldened to take action themselves which could take place anywhere in the UK. We are asked to continue to remain vigilant 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 MI5 . What the threat levels 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