Bletchley Park.
The estate of Bletchley Park is most famously recognised as the place where most of the German Enigma code was cracked in World War 2. It was originally a farmhouse which was extended to become the mansion it is today by London financier Sir Herbert Samuel Leon and remained his family home until the death of his wife in 1937, then the estate fell into the hands of property developers. There was a growing need for housing space due to the fact that London was grossly overpopul