Five stars overstates it somewhat. However, I thoroughly enjoyed it. A/A-
This was the first feature that I have seen with Jessie Buckley. She reminded me of Debbie Reynolds. Olivia Coleman gives her usual brilliant performance, but the whole main cast excelled, from Jessie Buckley on down. Special mention to Joanna Scanlan and Anjana Vasan, but really, there are no weak players in this cast.
Well-written and filmed. Standout cast. It's hard to beat. That said, it's set in a period, but it's not really a period piece. It includes some elements of a police procedural, but it's not that, either. It's a broad comedy about an amusing bit of history. It irreverently mocks manners, rectitude, racism, the Keystone Kops, pompous prosecutors, politicians and tabloid journalism.
So... It's quasi-historical but not history, satircal but not satire, broadly comedic but not exactly a comedy. What's left? It's a broadly comedic take on what happened, not a whodunit, so the players aren't the central focus in themselves. Lurking in the background are all sorts of things that should be taken seriously.
In a nutshell, I'd call it an absurdist farce. Not everyone will like it. A few will actively dislike it. I liked it--a lot--but maybe I'm just no longer in the mood to complain.