MI5 at The National Archives

MI5's files at The National Archives

You can learn more about this history of MI5 at The National Archives. 

The National Archives website provides a full overview of the most noteworthy files released from April 2000 onwards. 

We periodically release files to The National Archives. Some of the files we release are redacted to ensure sensitive information has been removed, and some individual documents may be retained for the same reason. Find out more about the policy on our Managing Information page. 

MI5 files in The National Archives cover many aspects of our work. They fall into categories, which can be found in The National Archives’ catalogue under five headings and KV is the catalogue reference for the MI5 in general. 

The headings are: 

• KV1 - First World War historical reports and other papers. Includes some of the earliest Security Service files from the time of its establishment as the Secret Service Bureau, as well as documents relating to the roundup of German spies in World War I. 

• KV 2 - personal files. Most of the files that we have released to date are in this category. They relate to specific individuals who were being investigated for various reasons concerning national security - generally relating to suspected involvement in espionage or subversion. 

• KV 3 - subject files containing papers on various national security issues. 

• KV 4 - policy files dealing with a wide range of matters such as Security Service liaison with other agencies. 

• KV 5 - organisation files relating to specific groups and organisations investigated for national security reasons.