October 2025

Today GCHQ is an independent British intelligence organisation. However during World War 2, GC&CS, as it was then called, continued to be subordinate to the British Secret Intelligence Service, known as SIS or MI6. The Chief of SIS was also the Director of GC&CS.

In this episode, we explore the relationship between the two organisations, the part that SIS played in supporting GC&CS, and the ongoing presence of SIS at Bletchley Park itself. Head of Content, Erica Munro, is joined by our Research Historian, Dr David Kenyon, and by a special guest - historian and expert on the wartime history of SIS, Dr Claire Hubbard-Hall.

To see the objects we discuss in this episode, visit https://www.bletchleypark.org.uk/our-story/e184-the-sis-at-bletchley-park/ 

Claire’s book ‘Her Secret Service: The Forgotten Women of British Intelligence’ is available from all good bookshops.

Image: ©Bletchley Park Trust 2025

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