'My dear Noel, I don't know what to write to you so I shall tell you a story about four little rabbits whose names were - Flopsy, Mopsy, Cottontail and Peter.' So begins Beatrix Potter's most celebrated letter, in which she tells for the first time the story that was destined to make her name famous all over the world, The Tale of Peter Rabbit. It was written to cheer up a sick little boy when he was ill, and is one of numerous surviving letters written by Beatrix Potter to entertain individual children. Sometimes her letters take the form of a supposed correspondence between different animal characters from the stories, each written in miniature with its own tiny envelope.