CabWarRm Next Cabinet War Rooms  

    Churchill talks to President Roosevelt or Truman (I forget which--one can listen to a reading of the transcript of the call) from the Transatlantic Telephone Room.

"The British method of disgusing the top secret function of the room was to install a toilet lock on the door--resulting, so it is said, in staff believing the room contained the only proper toilet in the site, which would inevitable be the PM's!" (From the guidebook "Churchill Museum and Cabinet War Rooms.")