Doing a bit of research preparatory to writing some comments about this movie, I discovered that Richmal Crompton wrote many stories about William and his pals from the 1920s until her death in 1970. They were, apparently very popular in Britain, and two movies were made in the late forties starring William Graham as the eponymous scamp. In this, the second movie, William goes to London to consult with the pleasant and vague Minister for Economics A.E. Matthews about having Williams' father fix the country's problems, brings a monkey home, then goes to the circus to get Mr. Matthews to write a note to get him out of trouble.
Everyone seems to live in that vague sort of middle-class world in which people keep comic servants and complain about money, where young boys dress in short pants, ties, and schoolboy caps which make perfect targets for water bombs dropped from the third floor, nothing bad ever really happens and no one ever quite learns a lesson, despite frequent beatings by the paterfamilias, played here by never-quite-apoplectic Garry Marsh. It's filled out with monkeys, circuses and roller coasters, and there are nice small comic bits for Jon Pertwee and Norman Pierce.
And elephants! It's all very pleasant harmless fun and must have been very comfortable for young parents who had first met William when they were children themselves, to find him just the same as they remembered him.
