Hello....You say that you are suspicious about this one....the position? Did you locate it from the OS Map?
Perhaps it has been moved from the original position.
Usually these pillars are to be found in elevated spots to enable the surveyors, in past times, to 'build up' the early maps.
My own experience with these in the Scottish hills is that they a fading feature and are not now kept in good condition as they are now no longer needed. Many of these, as I have found, are disappearing from the high tops and I have found bits and pieces of these around on or near to the summits.
I wonder if some folks now take them away as souvenirs of the past to have around in the garden.
Although definitely not exactly easy bits of furniture to transport.