It was a T.V. series, not a big budget film, but you wouldn't think that once you have started to watch it. The episodes manage to cram in so much, and range so far and wide, that you really get the impression of a country at war at a variety of levels.
A literate script deals with the different aspects of the story lines with economy and fluency. Care is taken to create a period atmosphere that looks authentic, there is good characterisation (even the fascist sympathiser is seen as a well rounded person with his own motives), and excellent acting......but it doesn't stop there.
The Dunkirk episode manages to create an evocation of a mighty event so successfully, and on such a limited budget, that it bears comparison with the sequence in Atonement.
One of the best things that British television has produced in recent years.