What did GCHQ green plaque do at this location?

The Story

# GCHQ's Hidden Genesis Standing before this unassuming London address, you're gazing at the birthplace of British signals intelligence as we know it today. Between 1919 and 1921, this building housed the freshly formed Government Code & Cypher School—a revolutionary merger born from the ashes of the First World War, when the Admiralty's legendary Room 40 (which had cracked German naval codes and intercepted the infamous Zimmermann Telegram) joined forces with the War Office's MI1(b) codebreaking team. Here, in these walls, Britain's scattered cryptanalytic brilliance was consolidated into a single organization for the first time, establishing the institutional foundations and tradecraft that would define the nation's intelligence capabilities for the next century. Though modest in appearance and brief in tenure at this location, this address marks the crucial moment when Britain transformed ad-hoc wartime codebreaking into a permanent, professional intelligence apparatus—a legacy that would prove decisive during the Second World War and beyond, eventually evolving into the GCHQ we know today.