To put it simply "The Admirable Crichton" is one of those delightful comedies which Britain use to make in the 50s, so delightful that even now 50 years after it was made it is still good fun. And that is all there is to it because whilst the storyline is about role reversal within the social classes it doesn't get deep, just has fun with the idea of a Butler basically becoming Lord and those he served end up serving him. Add to that the fun of being washed up on an uninhabited island and you have what is simply a charming, fun and hugely memorable movie.
As Lord Loam's (Cecil Parker) butler Crichton (Kenneth More - Genevieve) knows his place and wouldn't have it any other way despite Loam's claims that all are equal. But when Loam, his daughters, suitors, Crichton and maid Tweeny (Diane Cilento - Hombre) end up shipwrecked on an uninhabited island roles are reversed as it becomes apparent that without Crichton Loam and his family are helpless.
There isn't really much you can say about the storyline to "The Admirable Crichton" because it doesn't have a purpose. What I mean is we have this storyline of Crichton the loyal butler to the Loam's who sees it as his duty to serve, but when they end up washed up on an uninhabited island his leadership ends up making him everyone's Gov and the Loam's ending up serving him. That is really all there is to it, the fun from the role reversals, well that and typically a bit of romance as Crichton finds himself torn between Tweeny his equal and Mary the daughter of Lord Loam. Whether or not J.M. Barrie's satirical stage play of which this is a movie adaptation of makes any statement on social classes I don't know but there is no real statement made here.
What this means is that "The Admirable Crichton" is all about the fun be it at the start as Crichton loyally serves Lord Loam, making sure everything is perfect for his boss or when having been abandoned it becomes clear that Crichton is superior to his masters. It's impossible not to laugh when on the island as Crichton tries to salvage useful things from the ship wreck only to have to salvage luxury items for his snobbish bosses. And you laugh just as much when Lord Loam and his daughters realise that they are helpless without him. Throw in the fun of the wonderful contraptions they build on the island such as a water powered record player as well as a way to have heated running water and you end up with a huge smile on your face.
A big reason why you have that smile is down to two important pieces of casting that of Kenneth More as Crichton and Cecil Parker as Lord Loam. Both create great characters and make them fun especially when the roles are reversed, keeping the camaraderie going of two people who are close friends but one works for the other. Add in several fun performances from the various women including Diane Cilento's cockney sparrow Tweeny and Sally Ann Howes' beautiful Lady Mary and there is barely a scene which doesn't make you smile.
What this all boils down to is that "The Admirable Crichton" is a wonderful slice of 50s British comedy and if you are fan of Kenneth More or 50s British comedy it is a must watch.