Shtick in France
Entertainer Jack Millett (Jack Hulbert) is approached by Sir Jeffrey Arlington (Cecil Parker) as he has a rather unusual request. He wants him to head to the South of France to spy on someone, a friend of Jack's, Carole Markoff (Leonora Corbett), and if need be get close to her. There is one small problem, Jack's wife Kay (Cicely Courtneidge) who doesn't believe for a minute when Jack tells her the doctor has ordered him to go on holiday on his own and so follows him to France to spy on him.
On paper I could describe "Under Your Hat" as one of those movies which features some confusion comedy combined with the inept efforts of a man to act as a spy whilst dealing with his wife who is snooping on him. And when described like that "Under Your Hat" could be a comedy which say Steve Carrell or Jack Black could star in if it was made now. But "Under Your Hat" is a product of 1940 and is filled with the sort of stage comedy of the era with Jack Hulbert and his wife Jack Hulbert delivering dialogue so quick that at times you miss some of the gags. It also has some musical numbers tossed in there as well which of course are meant to be amusing. But it is a style of entertainment which to be frank doesn't work that well now and that makes this more of an example of what once passed for comedy.
What this all boils down to is that "Under Your Hat" ends up something of a lesson in British comedy from 1940, the sort which featured veteran entertained delivers the same shtick they had entertained audiences with for years.