Surely this is a sparrowhawk. Hen harrier would have three broad dark bars across the secondaries, including a very broad one at the trailing edge. This bird has 5/6 very narrow bars and no trailing edge to speak of.
Indeed, I couldn't reconcile any of the plumage features (remige pattern/extent of barring), shape and extent of the bands on the primaries, shape and size of the bands on the tail with Hen harrier, but the face kept throwing me off.
Time for cider, or ice cream, or both!