Bumped up to the top, as it is only on offer until midnight tonight... I'm sure more people are interested in it.

My wife's parents lived just outside the walls of Bletchley Park when they were newly weds, and although they knew there was some pretty secret work going on there they had no idea what it really was until the information finally became public knowledge in the mid 1970s.

It's a fascinating place, and the people who run the museum and maintain the buildings are extremely knowledgeable. Well worth a visit if you are in the area - not often you get to see an enigma machine in the flesh, as it were. There's also the National Museum of Computing there, so it's a double treat.