Reporting A Threat in UK
London's Scotland Yard Counterterrorism Office
-- Should you ever see a specific threat of an attack announced for London
-- the contact information for Scotland Yard on terrorist threats is as follows:
-- Telephone (from UK): 0800 789 321
-- Telephone (from U.S.): 011 44 800 789 321
-- Website: http://www.met.police.uk/so/at_hotline.htm
UK's MI5 Security Service
-- Reporting suspected threat
https://www.mi5.gov.uk/output/contact-us.html#01
https://www.mi5.gov.uk/output/contact-form.html?subject=Reporting%20suspected%20threats
-- Telephone (from UK): 020 7930 9000
-- Telephone (from U.S.): 011 44 20 7930 9000
-- Note that the MI5 telephone is not available 24x7, and if you uncover information of an urgent matter for a UK threat, you should contact Scotland Yard directly
-- Should you ever see a specific threat of an attack announced for London
-- the contact information for Scotland Yard on terrorist threats is as follows:
-- Telephone (from UK): 0800 789 321
-- Telephone (from U.S.): 011 44 800 789 321
-- Website: http://www.met.police.uk/so/at_hotline.htm
UK's MI5 Security Service
-- Reporting suspected threat
https://www.mi5.gov.uk/output/contact-us.html#01
https://www.mi5.gov.uk/output/contact-form.html?subject=Reporting%20suspected%20threats
-- Telephone (from UK): 020 7930 9000
-- Telephone (from U.S.): 011 44 20 7930 9000
-- Note that the MI5 telephone is not available 24x7, and if you uncover information of an urgent matter for a UK threat, you should contact Scotland Yard directly