Margaret Wilson is one of the remaining few who manned the wires at Bletchley Park during WWII, where she worked as a radio operator listening to German broadcasts for clues and encoded messages. And she's still not saying anything about it because her boss said not to.
Margaret's upper lip stiffness was tested in 2013, when she was invited to Bletchley for a reunion of staff, back when the current operators of the estate decided to name and publicly thank workers who put in the hours as part of the secretive war decoding effort. A group of "bigwigs" met her and told her it was OK to talk about it now as the war's been over for a while and we're almost friends with Germany now, but she was having none of it. Just in case.
She said of her meeting: "They say 'Margaret, you can tell us' and I say, 'You were not the one sworn to secrecy and told never, ever to disclose it to the end of your days'." She added that her boss at the time warned her the enemy might try to use exactly that sort of deceptive tactic to get it out of her, so even at 95 she's doing her part for national security and staying quiet, despite her family and historians joining the effort to get Margaret to tell her old Bletchley stories. [BBC]