May look like a picture of a windmill, however, would like you to look at its base which is in fact an iron age circular grave, they simply built the windmill on top of it to catch the wind (as Donovan would say)
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Certainly a bit different to a bloody 'walkers' shelter'. Windmills of the mind.
Better than the one on St Mary's in the Isles of Scilly: themodernantiquarian.com/post/21392/buzza_hill.html