I applied to Heritage England for the Newlyn Tidal Observatory to be listed as a building of interest. After months of research and consultation with associated bodies the HE emailed me just before Christmas 2018 to inform me that the Newlyn Tidal Observatory (and the stilling well) are now a grade II listed building and will be protected for generations to come.
I asked HE if they would/could “List” Bench Marks? but they said that they could only list the actual building/structure and not the BM. I would think that most of the bench marks that I have visited were on common or garden buildings (although from that time period between 1840s to 1980s) that I do not think would be eligible for listing (apart from the fact that they do have a bench mark on it of course).
This to my mind is a great shame as all BMs are historic in their own right and whatever their condition should be considered a very significant part of our industrial heritage.