>>Hi, Tony, Thanks for more lovely photos.  So nice to see the humble buttercup honoured. Ours are magnificent too!
This is about the square stone slabs that are used as field markers.  Down south, where I used to live, I had never seen such things, but when I moved up here and started serious walking, I saw them everywhere.  I asked one of my walking group if they had a name.  He said they were "vacheries" - derived from Old French for cow, it appears.  The name was then applied to cow pens (or folds, I suppose).
And of course with all the stone and slate quarrying up here, there were plentiful sources for the slabs.
I think they look very distinctive and they fascinate me.  I like the name too. 
Thanks again, Inga