Well, it’s whatever one properly calls the daughter of a Duke. It may be just “Lady Cambridge” for the time being. As an American, I wouldn’t know. I didn’t plan this (honestly!) but I happened to arrive at Paddington Station a half-hour after that the announcement that the Duchess of Cambridge had given birth. I was within a block of the Lindo Wing of St. Mary’s Hospital, and the celebration was just beginning.
Welcome, baby Cambridge!