Who is Lilibet?
The Queen, when Princess Elizabeth, was called "Lilibet" by her close family, a nickname that she earned because she could not pronounce her own name, Elizabeth. Her father, King George VI, used to say, "Lilibet is my pride. Margaret is my joy." As such, the nickname Lilibet has been with The Queen all of her life, and even her husband and confident, Prince Philip, is thought to refer to her by her childhood family name.
Indeed, Her Majesty, The Queen used to sign off her letters to friends and family with her nickname. In one letter that she had sent to her grandmother, Queen Mary, Princess Elizabeth wrote: "Darling Granny. Thank you very much for the lovely doll's house. I do love it, and I have unpacked the dining room and the hall. Love from Lilibet xxx."
A copy of this letter is shown below. Letter - Crown Copyright - The Queen 2016.