H. tuberosus hs 10 petals (not really petals, but you know which bit I mean) and yours has 12. The leaves on H. tuberosus are darker green and less toothed than yours. I am still looking for a certain id for you, but I still think it is H. x laeteritus which is a wild occurring natural fertile hybrid.
We have those here. I always thought that the size of the blooms were a disappointment after watching the stalks grown so tall. I had expected a much larger bloom!
