Met a lady in the UK recently, friend of my brother, who had done a guided tour of Bletchley Park the WWll spy/code breaking place (read Enigma). As the guide explained how the model of the Enigma machine worked, by moving cogs, she spoke up and told him he was doing it wrong and corrected him. Her husband was embarrassed and said not to talk about things about which she knew nothing. She responded that she used to work there during the war and worked on the Enigma machine. Her husband was stunned and said you never told me in many decades of marriage and what's more he used to work there too, but they had never met. That's keeping your mouth shut.
Wow, that would be an interesting person to talk to over a few drinks. I've watched a few documentaries about Bletchley. Evidently they got so good at it, there was a running joke that Bletchley knew German soldiers' orders before they even received them!