Catalogue description Government Code and Cypher School and predecessors: Personal Papers, Unofficial Histories, Foreign Office X Files and Miscellaneous Records

This series contains correspondence, working papers and initial drafts of both official and unofficial histories of British signals intelligence (sigint).

The records focus on prominent individuals and events, such as the deciphering of the Zimmerman telegram of January 1917 which was instrumental in persuading the United States of America to enter the First World War, and the transfer of the Metropolitan Police signals intelligence unit to Government Code and Cypher School control. The series includes a number of Foreign Office files concerning the transfer of the School to its control with details of its administrative history, and papers of WF Clarke, head of the Naval Section of the School in the inter-war years.

Admiralty, Government Code and Cypher School, 1919-1922

Foreign Office, Government Code and Cypher School, 1922-1946

From 1995 Government Communications Headquarters