The Queen has issued a Letters Patent decreeing that, if the unborn baby of the Duke and Duchess of Cambridge turns out to be a girl, she will be a princess and be styled Her Royal Highness.
This removes an anomaly that was contained in a decree issued by George V in 1917, which stipulated that a son would become a Prince but that a daughter would not become a Princess.
A Letters Patent is an open, public proclamation by the monarch, an official communication that is older than Parliament, and over which Parliament exercises no authority. There is no singular “letter patent”, it is always in the plural, akin to the royal “We.”
In his decree, the King had stipulated that the titles Royal Highness (HRH) and prince and princess should be restricted to the children of the sovereign, the children of the sovereign’s sons, and the eldest son of the eldest son of the Prince of Wales and that other daughters were to be known as “The Lady” plus title.
George V did this because he was worried about the growing number of people claiming to be princes and princesses, and he particularly wanted to discourage his many German relatives who’d become unpopular in England because of World War I from overusing titles.
The Queen’s Letters Patent is worded as follows: “All the children of the eldest son of the Prince of Wales should enjoy the style, title and attribute of Royal Highness with the titular dignity of Prince or Princess prefixed to their Christian names”.
The Queen’s new Letters Patent was issued so that the Royal Family’s titles could conform to Parliament’s stated desire to do away with male primogeniture, and allow the first-born child to become the heir presumptive to the throne, regardless of sex.