Room 40

room-40In the BBC’s ‘Battle of Jutland: The Navy’s Bloodiest Day’ documentary, televised earlier this year, Dan Snow tells the viewer:

In a room here in the Admiralty that was so secret some in the Naval hierarchy couldn’t even work out where it was, a group of code breakers was working on intercepted German messages.

Great story, you say! The inspiration for this state of affairs, incredible if true, seems to have been a parody called Alice in I.D. 25 (the section of the Naval Intelligence Division which Room 40 was part of by War’s end). ‘Alice started to look for Room 48. Room 49 was quite close, but none of the other numbers appeared to have anything to do with one another’. Alice must have been quite thick, as rooms in the Old Building (now known as the Ripley Building) were numbered strictly in a clockwise manner. Room 48 was 13 feet away from Room 49, on the same stretch of corridor. Rooms in the other Admiralty blocks, I, II, III (renamed North, South and West in 1917) were numbered anti-clockwise. Entries in the Admiralty Telephone Directory (see Room 40’s entry in the 1915 phone book below: Hope was the naval head of Room 40 till 1917) show clearly which block a room was in next to its number. The floor plans of the Admiralty let a historian know exactly where the rooms were in relation to each other. One thing is abundantly clear: If you were one of the privileged people to know of the existence of the Royal Navy’s codebreaking effort, you would know where the room was.


Lest anyone think that Room 40 was difficult to get to, it is a little over 40 feet down the corridor from the Old Board Room (Room 36) in which Snow and Admiral Lord West are shown talking in the documentary. All Snow had to do to get there was turn left. So Dan, for your next foray into naval history, please get some decent researchers, and don’t repeat tired old myths.

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