I'll go with Natalie Dormer;. The Tudors made no pretensions about what it was; enjoyable historic fluff.
My problem with Wolf Hall is that- whilst it was well acted throughout- it was a complete revisionist history, skewed by a historical writer with a specific agenda; It ends up coloring all my views about the acting involved and about how believable it is.
I didn't rate Natalie Portman that much in 'The Other Boleyn Girl' but tbh I rarely find her believable in anything, never mind a historical drama.