The current level was reduced to '' ' Severe ' '' on the afternoon of 17 September 2017 . It had been raised to '' ' Critical ' '' following the Parsons Green bombing on 15 September . The previous threat level to that was '' ' Severe ' '' having been reduced to that level following an increase to '' ' Critical ' '' after the Manchester Arena bombing of 22 May 2017
Manchester Arena bombing
Manchester Arena bombing
UK Threat Levels