https://homeofficemedia.blog.gov.uk/2018/08/16/scale-of-the-terrorism-threat/

Scale of the terrorism threat

Following the incident in Westminster on Tuesday the Home Secretary and Security Minister have paid tribute to the professionalism of the emergency services who were immediately on the scene.

As set out in our Counter Terrorism strategy CONTEST the scale of the multi-faceted threat we are facing is both increasing and evolving. The police and Security Service work tirelessly to keep the public safe and disrupt all forms of terrorist activity.

They work closely to combat the threat and it is testament to their efforts that 13 Islamist and four extreme far-right terrorist plots have been successfully foiled in the past 18 months.

At the end of June 2018 there were over 650 live investigations across all forms of terrorism. Police and MI5 are working together on over 500 of these investigations, and there are over 100 unique to CT policing.

The threat we face is diverse, the number of live investigations constantly fluctuates and not all investigations will involve the Security Service.