In Act II of Oscar Wilde's The Importance of Being Earnest, Algernon and Cecily have this exchange:
Cecily: I can't understand how you are here at all. Uncle Jack won't be back till Monday afternoon.
Algernon: That is a great disappointment. I am obliged to go up by the first train on Monday morning. I have a business appointment that I am anxious . . . to miss?
Cecily: Couldn't you miss it anywhere but in London?
Algernon: No: the appointment is in London.
What is the humorous meaning behind these lines?