The following story was recounted by Princess Marie Louise, grand-daughter of Queen Victoria, and is recorded in The Faber Book of Anecdotes:-
This prompts me to reflect that there are, amongst teachers, two types of cleverness. There is, on the one hand, the person who makes the listener think: “He must be very clever; I don’t understand a word of what he is saying.” Then, on the other hand, there is the teacher to whom people respond: “Now I understand! I’m not so stupid after all!”
I know which type I would rather be.