First class TV. What I have come to appreciate is that there are no "fillers" in the dialogue and plot. It is very carefully written so that everything said has some bearing on the ongoing shift in social and class structure that is taking place. Good cast. Good production. Nothing bad to say really. And I am not a general fan of period movies/TV.
We've watched it to the end of series 3, and I'm pleased to hear that they will shortly start filming series 4.