Probably the last man who knew how it worked had been tortured to death years before. Or as soon as it was installed. Killing the creator was a traditional method of patent protection.
Uncle Bub: Did you know that I invented the peanut butter and jelly sandwich?
Timothy Green: Did you know that I’m a big fan of your work?
Dowager Countess: Good heavens, what am I sitting on?
Matthew: A swivel chair.
Dowager Countess: Another modern brainwave?
Matthew: Not very modern, they were invented by Thomas Jefferson.
Dowager Countess: Why does every day involve a fight with an American?
Matthew: I’ll fetch a different one.
Dowager Countess: No, no, no, no – I’m a good sailor.