I dont know what this plant is ---

-- but the hover flies love it.
We celebrated our 57th wedding and stayed overnight at "The Pudding Club" in Mickleton. Being so close, we couldn't leave without visiting the NT gardens at Hidcote (and buying a couple of plants).
The hover flies on this plant were so numerous that taking just one was impossible, trying to get one in flight meant accepting that there would be several others both in and out of focus.