Continuing the discussion in the Lady Jane Grey thread about whether it's possible for there to be a female Heiress Apparent (rather than Heiress Presumptive), and the scenario which makes this possible (if the heir apparent to a reigning monarch dies having left daughters but no sons, in which case the eldest daughter couldn't be displaced by any later-born royal children and would thus be Heiress Apparent), I was wondering if this means that an Heiress Apparent would be eligible to be created Princess of Wales in her own right.
From what I've been reading about the title, "Prince of Wales" can be bestowed only on the Heir Apparent. So far in history all our female monarchs were previously Heiresses Presumptive, which if I remember right is the reason why George VI refused to make Princess Elizabeth Princess of Wales.
There are a lot of scenarios when a female can be Heiress Apparent, although it is certainly more common to have a male Heir Apparent.
If, for example, William were to have only one daughter and predecease his father, it would be perfectly obvious that the girl is Heiress Apparent.
However, she would not be invested as "Princess of Wales" in her own right, as the title would be
inferior to her title of a Princess of the United Kingdom (as of current situation). This is because the title of "The Princess of Wales" in its female form simply does not exist; it is merely a courtesy title held by the wife of the Prince of Wales. In order for this to be changed, Legislation(s) and Letters Patent are to be introduced.
There is a scenario where Heiress Apparent would likely be invested as Princess of Wales in her own right without the need of Legislations or Letters Patent (regarding the Princess of the United Kingdom title, that is), and the title would not be inferior to the one she already holds. If William were to die, leaving sole daughter in Queen Elizabeth II's lifetime, his daughter would not automatically be Princess of the United Kingdom, as she wouldn’t be male-line grandchild of the Monarch (not that it is likely she wouldn't be created one upon or even before her birth, but it is possible she isn’t by the time of William's death). In that case, a decision might have been made to invest her as Princess of Wales, rather than grant her the style and title of the Princess of the United Kingdom. Both outcomes would require Letters Patent.
<>... So far in history all our female monarchs were previously Heiresses Presumptive... <>
There was actually a case in English History when a female was considered Heiress Apparent - Henry VIII's daughter Princess Mary. When it became apparent he will have no legitimate male Heirs from his marriage to Catherine of Aragon (and before he started having 'doubts' about the legitimacy of the marriage), Henry bestowed Mary with many of the rights and properties traditionally given only to the Prince of Wales, most importantly, t
he official Seal of Wales for correspondence (some of Mary's correspondence sealed with the Seal survive to this day). During that period, she was often referred to as Princess of Wales as well.
While Mary was never
created the Princess of Wales, she was closest a female ever got to, and that includes the present Queen.
But since it's at least theoretically possible for there to be an Heiress Apparent - such as, for example, if some awful accident wiped out Charles, William, Harry, and Andrew before any of them had any more children - then I wonder if the title would be bestowed on Beatrice.
If some terrible accident like the one you mentioned indeed happened and a female was left as an Heiress Apparent, I believe Legislations
would be passed and Letters Patent
would be issued to grant her all the titles and style befitting Heiress Apparent, including the title "Princess of Wales" in her own right. The Letters Patent would have to specify that her title of the Princess of Wales would not be inferior to her title of "the Princess of the United Kingdom".
If it comes to a situation like that, then it would be only one step to adopting Equal Primogeniture, in which case a female title of "The Princess of Wales" would be created, so that the Heir(ess) Apparent of the Sovereign, regardless of gender, is invested as Prince(ess) of Wales.
That would open another issue, of course; question of the titles of the spouse of the Prince(ss) of Wales.