Fans have been saying for years that Bill Murray would make a great President. Now the honchos in Hollywood have listened and cast him as Franklin D Roosevelt in this period dramedy that mixes fact and fiction, May-to-December romance, Downtonesque shenanigans and the story of Britain's King George VI and Queen Elizabeth's visit to the US in June 1939 - the first by a reigning British monarch.

The film is based on the true story of Daisy Suckley, a fifth cousin of FDR's, and the suitcase full of letters and diaries found under her bed when she passed away, aged 99. Here, Daisy is played by Laura Linney who, incapable of giving a duff performance, brings a genuine poignancy to Daisy's devotion to FDR, and her vulnerability.

She lives near FDR's summer residence at Hyde Park on Hudson in upstate New York and becomes part of the inner sanctum - his unconventional relationship with wife Eleanor (Williams), his never-grew-up relationship with his mother Sara (Wilson) and his eye for the ladies. All this and the newly crowned King's arrival to contend with, too.

The King (West) is coming because, with war looming, he needs the US' help. He's new to the job, extremely low on self-confidence and both he and his wife (Colman) think the Yanks are poking fun at them. They're not; and over a fateful weekend we see how that special relationship between the US and Britain was forged, as FDR also tries to contend with drama galore in his personal life.

Murray's career is full of class performances and his turn in Hyde Park on Hudson is as unusual as it is great. Eschewing the deadpan comedy and playing it straight, his avuncular take on Roosevelt shows that he should do more serious stuff. On this evidence, his best could be yet to come. And there's many a time here that you actually forget you're watching Bill Murray - his portrayal of FDR is so charming, warm and tender that you almost forgive the President's on-screen behaviour. The Royals are also sent up, celebrated and humanised, with the dilemma of staying in someone else's house for the weekend providing most of the laughs.

The personal and political don't always fit - sometimes things are a little slow and uneven - but Hyde Park on Hudson manages to be a movie that has treats for slackers and elderly aunts. And when Murray and Linney sit in a car in a meadow listening to Moonlight Serenade you may be feeling the exact same way in the cinema.

Harry Guerin