Cardiff University professor Brian Ford says he uncovered the plan while reviewing recently declassified documents for his new book, Secret Weapons: Technology, Science, And The Race To Win World War II.
British spies figured that if they could lace Hitler's food with estrogen, over time he would become less cruel and aggressive, Ford says. The idea was to "feminize" Hitler, and make him behave more like his sister, Paula, a "mild-mannered secretary." The Brits were encouraged by then-recent research into the effects of sex hormones in therapy. "There were agents who would be able to get it into his food," Ford says, as quoted by The Telegraph. "It would have been entirely possible."
No one ever put the plan into action, probably because it was crazy--just like some others highlighted in this article over on The Week. Link