Ask the Chatbot Games & Quizzes History & Society Science & Tech Biographies Animals & Nature Geography & Travel Arts & Culture ProCon Money Videos
MI5
Table of Contents
Introduction References & Edit History Quick Facts & Related Topics
Read Next
Union Jack flag of Great Britain, united kingdom
What’s the Difference Between Great Britain and the United Kingdom?
Text Top Secret typed on retro typewriter
How Secret Is Top Secret?
Rural Irish landscape, Sligo, Ireland.
Why Is Ireland Two Countries?
King Charles III and Queen Camilla (Camilla, Queen Consort) wave from the balcony of Buckingham Palace during the Coronation of King Charles in London, England on May 6, 2023
British Royal Line of Succession
Communism - mosaic hammer and sickle with star on the Pavilion of Ukraine at the All Russia Exhibition Centre (also known as VDNKh) in Moscow. Communist symbol of the former Soviet Union. USSR
Why Did the Soviet Union Collapse?
Discover
Aspirin pills.
7 Drugs that Changed the World
Cathedrale St.Jean in Lyon, France has a 14th-century astronomical clock that shows religious feast days till the year 2019; Perpetual Calendar
Ten Days That Vanished: The Switch to the Gregorian Calendar
Drinking water is poured into a glass.
Water Fluoridation: Just the Facts
Poker game. Card game. Royal Flush in poker. Hearts suit gambling
Poker Hands Ranked
Happy, smiling, flying pig
7 Everyday English Idioms and Where They Come From
Aurochs. Bos primigenius. Skeleton. Extinct animal. Skeleton of an Aurochs, an extinct wild ox.
6 Animals We Ate Into Extinction
Periodical Cicada, Adult, Magicicada spp. Requires 17 years to complete development. Nymph splits its skin, and transforms into an adult. Feeds on sap of tree roots. Northern Illinois Brood. This brood is the largest emergence of cicadas anywhere
Why Do Some Cicadas Appear Only Every 17 Years?

MI5: Facts & Related Content

verifiedCite
While every effort has been made to follow citation style rules, there may be some discrepancies. Please refer to the appropriate style manual or other sources if you have any questions.
Select Citation Style
Share
Share to social media
URL
https://www.britannica.com/facts/MI5
Written and fact-checked by
The Information Architects of Encyclopaedia Britannica

The Information Architects maintain a master list of the topics included in the corpus of  Encyclopædia Britannica, and create and manage the relationships between them.
The Information Architects of Encyclopaedia Britannica
Gerry Adams fights for peacemaker reputation in trial over BBC murdered spy claim • May 12, 2025, 7:26 AM ET (The Guardian)
Author Barbara Pym may have worked for MI5, research suggests • May 1, 2025, 3:32 AM ET (The Guardian)

Facts

Also Known As BSS • British Security Service • Security Service
Date 1909 - present
Areas Of Involvement intelligence • counterespionage
Related People Anthony Blunt

Related Topics and References

Topics