From the National Archives:
"This month sees the 100th anniversary of the Security Service, the UK's national security intelligence agency. Known for keeping personal files on a great range of individuals, the Security Service has released over 4,000 of these files to The National Archives since 1997.
The Security Service files cover a period up to the late 1950s and are open to the public. You can view many of them on our website, including those of Sidney Reilly, the spy thought to have inspired James Bond. Our new security history research signpost provides a good overview of the files, and offers some tips on searching them."
Do also note that the NA has revised its opening times and that from 4th January 2010, the NA will be closed on Mondays. Alright for some.