For a farce, this is actually quite entertaining - I'm not keen on broad humour, but this rarely goes over the top. Note that I say 'rarely' and certainly not 'never'!
The film opens with a vivid montage of London, with music winding out from a couple of down-at-heel players in a pub across street scenes, night life and even the river. Finally one of the characters we glimpse turns out to be our eventual protagonist -- a constable on 'point duty', guiding the traffic at a busy junction. But PC Mahoney has a sweetheart who is a lowly attendant at a nightclub, the Moonstone, and when she tips him off that there is an illegal gambling operation being operated above the club, he decides to take matters into his own hands and turn up to conduct an investigation in plain clothes in the hopes of getting promotion into the detective branch. Mahoney (who never loses his thick Irish brogue despite dressing up as a gentleman of means) is the most likeable and resourceful characterin the plot; Claude Hulbert plays silly-ass Aubrey, who is always eager to help but only ever seems to make things worse, and toothy Ralph Lynn plays Clifford Tope, who volunteers to pay off a blackmailer for the sake of a pretty stranger whose dancing appealed to him, but takes it into his head to try to confront the man instead, thus causing endless trouble.
The romantic interest, such as it is, lies between Tope and night-club star Cora, although since he is cowardly and not particularly intelligent (his only success lies in hiding behind a curtain and bopping Mahoney's assailants over the head) it's not clear that she feels anything for him beyond misplaced gratitude. Mahoney and his Molly, despite getting little screen time together, are much more endearing as a couple.
There's the obligatory scene where someone loses his trousers, which actually makes sense in the context of the plot; there's a sub-plot of a villain behind the villain, which leads to some amusing scenes. (Please can I blackmail her? Please?) Most of the funny parts involve the resourceful Mahoney talking rings round the other characters; a character being intelligent is always much more entertaining than characters being stupid. Likewise C.V.France, as the brains behind the whole gambling operation, gets the best lines out of the various villains, especially in the scene where he is attempting to interrogate three semi-conscious toughs as to exactly what happened to them.
The lanky Norma Varden and diminutive Robertson Hare make a study in comic contrast as Aubrey's redoubtable aunt and uncle with an eye for the ladies respectively; Mary Brough is Cora's gruff and indignant dresser, who has to put up with a succession of men in and out of the dressing-room and her mistress' flat. The on-screen dancing isn't particularly impressive by Hollywood chorus line standards -- apart from anything else the girls have very little room to play with! -- but Al Bowlly puts in a cameo appearance as the night-club's crooner.
The final scene ends with the villains being marched off en masse, followed by our victorious protagonists, which leads to a slightly surreal ending where the night-club audience and people in the street start applauding and the whole cast pauses and fans out down the front steps, heroes and villains alike, in what you eventually realise is the equivalent of the original play's curtain call. Otherwise the show's stage origins are not obviously intrusive and -- for a farce that features people getting bopped over the head, trapped in doors, and making eyes at pretty maids -- it's often genuinely amusing. The BFI bills this film as one of the best of the Ben Travers screen adaptations, and I can believe it.
