Hiya!
Have you ever heard about Reigate? It’s one hour away from Central London and really beautiful, there is a beautiful park and the most exciting: CAVES! It was the first time I have visited “urban caves”, those are caves made originally to extract sand. The most interesting fact about these caves is that it was used during the Second World War to hide from bombs and they keep loads of historical items as oxidised metal toilets, radio, notes on the walls and there is an entire museum full of items used during the World War such as radio, helmets, sheets giving information about Hitler, etc.
I have done a vlog about the place, you can check here: