So is it OK to call her Princess Kate now?

The Duke and Duchess of Cambridge have formally registered the birth of Prince George, and Kate is described as a Princess on the document.

William—whose occupation is given as “Prince of the United Kingdom,” and there we were thinking he was a helicopter pilot—signed the birth register at Kensington Palace this morning, witnessed by a registrar from Westminster Register Office.

We note that Kate—job title; Princess of the United Kingdom—was not there— presumably still sheltering down at her mom's and getting to know baby.

A palace spokesman tells me: "Prince William continues to be a Royal Prince. On marriage, Prince William retained the title Prince William of Wales and as the wife of a Royal Prince, the Duchess is entitled to use the name of her husband, Princess William of Wales. It is important to note she is not Princess Catherine so to call her that or Princess Kate would be incorrect."

However, it seems like it is OK to call her “the princess” when referring to her in the third person, which is much more fun, right? Who'd be a duchess when you can be a princess? I mean, why would you want the same title as Fergie?