Set in 1930's London, this is more of a vignette than anything . The settings are all kept to period, but cliche pervades and London is often foggy. Because of the story, everything is gloomy too. The story references, a little, the politics of the time, and can be seen referring to well
known British newspaper magnates.
So, the challenge, when you have well known actors who "act", is that any film they're in, in my view, looses a degree of authenticity and believability. I think this film suffers from that.
The main actors (Arterton, Mckellen) and the rest of the ensemble do a decent job, and the writing is of better quality than normal. However, I kept thinking that this is a stage play that doesn't translate well to film. I think the target viewer demographic are the sort of people who like to see serious stuff in the theatre, so this isn't one I would recommend, unless you like vaguely depressing, serious, cinema/theatre.