I actually came to Berkeley Square because of some other historical research I'm doing. The vault of the Bristol lodge of the Stella Matutina (an offshoot of the Hermetic Order of the Golden Dawn) is meant to have been destroyed in Berkeley Square, and I've been idly wondering which building might have housed it.
Not that there would be any clue left lying around now, of course, but it was fun to ponder on which door might have admitted you to the lodge, assuming they were ever actually based here. That's the problem with secret societies: it's quite hard to find things out about them.
The 23 attracted me as much as the colour of the golden door, given that it's a significant number for the Illuminati...
GPS Coordinates:
51.45545, -2.60577
Location: Tyndall's Park