The Public Records Act 1958 places a legal requirement on government departments to transfer records to the National Archives
30 years after creation. GCHQ has a blanket exemption from this requirement but has made voluntary releases which appear on the National Archives catalogue
under the HW series in eighty classes so far.
Release of Bletchley Park and other GC&CS records
A 10 year exercise to review and release the majority of surviving records belonging to the Government Code and Cipher School, was completed in 2004. Records released date from 1919 and the beginnings of GC&CS, then located in London, up to VJ-Day (16 August 1945), and covering all war time activity by then carried out from Bletchley Park
. This means that virtually all surviving SIGINT or SIGINT-related records from this period regardless of subject or target have been made available for public access.
Release of post-war historical records
HW15 contains records relating to VENONA, reporting on the activities of Soviet intelligence between 1942 and 1948, complementing a release made by the National Security Agency
in the United States. Additionally, a small release of post-War security records has been made and can be found in HW9.
Work is currently underway to review and release GCHQ intelligence reports dating from the early Cold war period, 1945-1950, on the Soviet bloc countries, Albania, Bulgaria, Czechoslovakia, Hungary, Poland, Romania, USSR and Yugoslavia.
Click on the image to enlarge:
Taken from HW 75/24
Some 4,000 of these reports have been transferred to the National Archives in a new series, HW 75, and further sets will be released in due course.