The Queen decreed before the birth of Kate, Duchess of Cambridge and Prince William's first child that all of their children would hold Prince or Princess titles. For this reason, Prince George, Princess Charlotte and Prince Louis all hold the royal style. But under the title rules dictated by King George V in a 1917 Letters Patent, previously only Prince George would have been eligible for a title if the Queen hadn't intervened.

       Princess Charlotte is currently styled as HRH Princess Charlotte of Cambridge, to reflect the title of her father as the Duke of Cambridge.

       But Charlotte and her siblings may undergo further title changes in the future, such as if their father becomes the next Prince of Wales.

       If Prince Charles gives William the title of Prince of Wales when his reign begins, Charlotte will likely become HRH Princess Charlotte of Wales.

       And Charlotte may also get a new royal title when her father is King, as she will then be the only daughter of the reigning sovereign.

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       Traditionally in the Royal Family, the eldest daughter of the sovereign holds the title of Princess Royal.

       The title is not automatically received and must be allocated at the discretion of the monarch.

       But as Princess Charlotte is Prince William's only daughter, there is a good chance Charlotte will get the unique honour in the future.

       The current Princess Royal is Princess Anne, and she received the title from the Queen in 1987.

       Anne will hold the title until she dies, and then the title will be left vacant.

       Charlotte could also get a new royal title if she decides to marry.

       In the Royal Family, royal titles to mark a marriage are usually given to men, and women take on the feminine equivalent title.

       If Charlotte marries a Duke or an Earl, she might expect to be known as a Duchess or a Countess.

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       As the eldest daughter of the sovereign, then-Princess Elizabeth would have been eligible for the Princess Royal title before she was Queen.

       However, the title was not vacant during the reign of King George VI, so Elizabeth could never be given it.

       Elizabeth's aunt and George VI's sister, Princess Mary, was Princess Royal until 1965.

       She received the title in 1932 from her father, King George V.

       As King George VI died aged 56 in 1952, Princess Elizabeth never had the opportunity to hold the title before she became Queen at the age of 25.

       When King George VI was alive, then-Princess Elizabeth was also never eligible for two other royal titles, despite being the heir to the throne.

       The heir apparent to the throne has usually been bestowed the Prince of Wales title by the reigning monarch.

       But the title is only given to male descendants of the monarch, so the Queen was never eligible to be the Princess of Wales.

       The Princess of Wales title can only be used by someone married to the Prince of Wales, hence why Princess Diana used the title.

       Princess Elizabeth was also not eligible for the Duchy of Cornwall, which is automatically inherited by a male heir to the throne.

       Prince Charles became the Duke of Cornwall automatically following the death of King George VI and the accession of his mother in 1952.