I forget the details, but I recall this video on the Colossus- a very secretive program that resulted in arguably the first programmable digital computer (iirc). I think we only relatively recently learned of it's existence?

https://youtu.be/g2tMcMQqSbA?si=bW059oO6B4H1GR_R

It was very worth the watch, lots of fascinating tidbits including some stories of unsung heroes / geniuses. It was kept secret even after WWII but the people involved went off to kickstart the computer industry in England