but she is not styled as Princess William or Princess Catherine. She is a princess (by marriage) of the United Kingdom of Great Britain and Northern Ireland.
Far too many people just do not get it. In Britain, a woman takes her husband's rank unless her rank is higher. Catherine Middleton emerged from Westminister Abbey as a princess ... but what ... she is not styled as a princess. Why you may ask? Easy. Her husband, William, is no longer styled as Prince William of Wales. His official title and style is now HRH The Duke of Cambridge.
Not HRH Prince William of Wales, Duke of Cambridge, but HRH The Duke of Cambridge. But he remains a prince because he is a grandson of the Sovereign in the male line. George V's 1917 Letters Patent, which limits the title of Prince or Princess to the children of the sovereign, the grandchildren of the sovereign in the male line, and the eldest son of the eldest son of the Prince of Wales. The Duke of Cambridge is a Prince. His wife is a Princess by virtue of the marriage.
It is amazing how dense some people can be. Learn to understand the difference between title, style and rank. Just because Catherine is not styled as a princess does not mean she is not a princess. If the Queen had not bestowed the dukedom on Prince William, Catherine would have been styled as HRH Princess William of Wales. William was styled as HRH Prince William of Wales because he is a son of the Prince of Wales. The daughters of the Duke of York are HRH Princess Beatrice and Princess Eugenie of York.
HRH The Duchess of Cornwall is also a princess because she is married to a prince.
According to several British news sources, William wanted Catherine to be STYLED as HRH Princess Catherine of Wales. I don't believe this story to be true. The Queen would have vetoed this because Catherine was not a British princess by birth, but by marriage. Princess William may sound antediluvian, but that's the tradition in the United Kingdom. HRH Prince Michael of Kent's wife is HRH Princess Michael of Kent. Even if Marie Christine were a princess in her own right, she would still be styled as HRH Princess Michael. Her title comes from marriage, not from birth.
When Princess Marina of Greece and Denmark married the Duke of Kent in 1934, she became HRH The Duchess of Kent. She was still referred to as Princess Marina, especially in the popular press, but Princess Marina was a Greek title, not a British one. She would have been styled as HRH The Princess George if her husband had not been created Duke of Kent. Shortly after the marriage of her eldest son, the Duke of Kent, in 1961, Marina, announced that she would now be styled as Princess Marina, Duchess of Kent. She needed the permission of Queen Elizabeth II to use this style because she was not a British princess in her own right.
[The late Princess Alice, Duchess of Gloucester, followed this precedent when the Queen allowed her to be styled as Princess Alice, Duchess of Gloucester, after the death of her husband. She was briefly styled as HRH The Dowager Duchess of Gloucester.]
William's new title makes him a peer of the realm, which means he is no longer legally a commoner. Yes, dear readers, princes and princesses in the United Kingdom are legally commoners. Only the sovereign and peers of the realm are not commoners, despite having the title of prince or princess. Even with his new title, he does not stop being a prince because he was born a prince. His official title is HRH Duke of Cambridge, but he remains a prince.
The media are largely ignorant about this. Many journalists will write Prince William and the Duchess of Cambridge. This is incorrect, as is Prince William and Princess Catherine, but, please do not get your knickers in a twist about this. Most readers do not (nor do they care) about the correct use of titles. The average person will continue to think of the couple as Prince William and Princess Catherine, and that's okay, too. Those of us who speak the language of royal titles will understand that the writers are referring to the Duke and Duchess of Cambridge. William has been known as Prince William for nearly 30 years. He needs to get used it as well.
Stop using Prince William and start using the Duke of Cambridge because that's his title now. His father is the Prince of Wales. His uncles are the Duke of York and the Earl of Wessex. They are princes. Camilla, Catherine and Sophie are princesses because their husbands are princes ... but remember, they are styled as the Duchess of Cornwall, the Duchess of Cambridge and the Countess of Wessex!
Catherine is not Catherine, Duchess of Cambridge. This style is reserved for widows of peers or divorced wives. HRH The Princess of Wales became Diana, Princess of Wales. HRH The Duchess of York is now Sarah, Duchess of York. It is not Sophie, Countess of Wessex or Prince Edward, Earl of Wessex, If Edward had not been given the peerage, his wife would now be styled as HRH The Princess Edward. Edward's a prince, Sophie's a princess but they are styled as HRH The Earl of Wessex and HRH The Countess of Wessex. No names included ...
When Lady Elizabeth Bowes-Lyon married HRH The Duke of York, the media asked the palace about the new royal bride's status. Lord Stamfordham responded: "In accordance with the settled general rule that a wife takes the status of her husband Lady Elizabeth Bowes-Lyon on her marriage has become Her Royal Highness the Duchess of York with the status of a Princess."