Near Nottingham is the Cotgrave Royal Observer corps Nuclear observation bunker. It’s in a wood across a few fields and quite over grown. It’s open and burnt out long ago. Nothing is left inside but an old bedstead. Whilst the field surrounding were fill of growth someone had been there recently as you could see where they had walked. These old bunkers attract a lot of attention now - pre internet few knew of them at all. *Need to know* seems to sum it up.