The Prince and the Showgirl is, naturally, quite a fantastical film. The regent of a fictional country, Grandduke Charles (Laurence Olivier), comes to Britain for the coronation in 1911. He has one free evening in the capital and decides to see a show at the Coconut Girl Club. He takes a shine to Elsie (Marilyn Monroe) and invites her up to the embassy for a little supper. Once Elsie realises exactly what he wants from this intimate supper she tries to escape but foreign officer employee, Northbrook (Richard Wattis), persuades her to stay. The next day she overhears a conversation between the regent's son, king-in-waiting Nicolas (Jeremy Spenser) and someone he is plotting an uprising with. Of course, she sets about trying to reconcile father and son and suddenly finds herself at the coronation courtesy of the Dowager (Sybil Thorndike).
This is a rather complicated film with some over-long scenes and fragments of dialogue that don't work particularly well with the assembled cast. Taken individually, Olivier is tolerable as the regent while Monroe puts in a very inconsistent performance as Elsie. There are moments which seem specifically tailored to recapture her innocent hilarity of earlier roles but the pieces just don't seem to fit together on this one. There are some genuinely funny moments involving Monroe, though the overall effect of her charm is diluted. Thorndike is, however, superb as the Dowager and I think Richard Wattis as the dry (and very English) representative of the foreign office stole the film for me.
Implausible plots are fine if the film has enough charm to carry it off. For me, The Prince and the Showgirl failed on this point. It seemed more preoccupied with showing off the London scenery than anything else - hence the long monotonous scene of Elsie staring at the ceiling of Westminster Abbey while the coronation was going on. There was no chemistry between Olivier and Monroe that I could see, though there was definitely a spark of something else there! All in all, a passable film but not one I'd actively go out of my way to rewatch.