The Bletchley Park codebreakers worked in conditions of extreme secrecy — the building was surrounded by barbed wire, guards checked all outgoing mail, and staff were forbidden from discussing their work, even with their families. But one lesser-known rule stands out: during particularly sensitive operations, staff were forbidden from drinking water, to prevent the need for bathroom breaks during critical decryption windows. Some staff developed urinary tract infections as a result. The reason: bathrooms were considered surveillance risks, with acoustic monitoring theoretically possible. Women in the codebreaking huts, who made up 75% of the workforce by 1944, were also required to leave their hair unpinned (so it couldn't conceal notes) and wore only approved stockings (to prevent contraband smuggling). These rules were enforced by a dedicated security staff that outnumbered the codebreakers 3 to 1.