Robert Altman's acclaimed and award-winning 2001 film Gosford Park is a whodunit that isn't really a whodunit. The first time I watched it, rather naively I focused on the whodunit aspect of the story and the plot, and found the film enjoyable but not quite the masterpiece it was supposed to be. Now I've taken another look at the DVD version, which includes some useful bonus features, and I'm even more impressed than I was originally.
Really, Altman took the idea of a Golden Age whodunit in a country house setting and used it as a context for a story about the class divide in the age of masters and servants. More or less everything is seen from the perspective of "below stairs", and the amateur detective work, such as it is, is undertaken by a servant. There's a lot of humour in Julian Fellowes' script, and there are many nice observations. I've never watched Downton Abbey, but there's no doubt he's a talented writer.
There is a large ensemble cast, and one of the doubts I had about the film originally is that this means that many of the characters are undeveloped. A large cast also makes it difficult to care about many of the suspects, and the plot of the story isn't its strong point, though there is a pleasing and inventive use of tropes such as the body in the library, the double killing, and impersonation. Stephen Fry's police inspector is amusing but buffoonish, perhaps excessively so.
As for that cast - wow! Michael Gambon, Maggie Smith (in brilliantly waspish form as the Countess of Trentham), Kristin Scott Thomas, Charles Dance, Tom Hollander, Geraldine Somerville, Jeremy Northam (as Ivor Novello!), Helen Mirren, Kelly Macdonald, Laurence Fox, Alan Bates, Clive Owen, Derek Jacobi, Emily Watson, Eileen Atkins, Richard E. Grant...There's a lot of pleasure to be had from simply watching such stars in action. I can recommend this DVD; it's definitely a film worth watching more than once.