I gave this film four stars--each for Monroe, who is at her dazzling comedic best here. The film itself is a slow period piece, lanquidly directed by Laurence Olivier, but MM breathes exuberant life into her every onscreen moment. Playing a character with some smarts and savvy, given wittier lines than usual, Monore simply walks away with the film. She is a vigorous American showgirl--healthy, vital, nobody's fool. If anyone possibly doubts MOnroe's ability to create character, compare this vital delectable performance with the weary, worn-out Cherie of "Bus Stop" filmed just months before. Both performances reveal facets of Monroe's talent she was never allowed to use again--not even in "Some Like It Hot." Dame Sybil Thorndike, playing Olivier's mother-in-law steals scenes from Monroe AND Sir Laurence! The coronation sequence is deadly dull and the ending--Monroe's rapid about face--is silly. But the film lives for her delicious high-spirits and wit.
Two other points--Monroe wears the most unforgiving gown of her career, a white number that she never takes off, which rather cuts down on much-needed visual variety. And the voice that she uses in the brief musical interlude is indeed hers; she has simply pitched it to a MUCH higher key! This is not as appealing as her her usual singing style, but appropriate for the period.
"The Prince and The Showgirl" is not Monroe's most famous role, but it is one of her greatest performances. And that she was able to create something that appears so effortless at a time of tremendous personal crisis (she miscarried during the film) stands as a testament to her oft-maligned professionalism.