I see it now Ian, quite a mystery, it appears to have an entrance near to the fence and is quite high , looking on Google Earth shows it has something circular in the centre and marks in the field lead down to the area of marsh grasses in that lower field as though a drain was installed . Your guess is as good as mine :o).
What kind of charming one a photo is!
We waited for the spring and the good time very much already!
THERE IS BIG FLOOD NOW UNFORTUNATELY!
My friendly greeting,Natuska from Hungary
Nice photo, I remember places LIKE this from my younger days. Greetings from Adelaide South Australia. Howie.
A Capstan always needs a light, Jim.