Sayers, Dorothy L. Unnatural Death.

Miss Climpson was one of those people who say: "I am not the kind of person who reads other people's postcards." This is clear notice to all and sundry that they are, precisely, that kind of person. They are not untruthful; the delusion is real to them. It is merely that Providence has provided them with a warning rattle, like that of the rattlesnake. After that, if you are so foolish as to leave your correspondence in their way, it is your own affair.