So how is it that Kate isn't actually a Princess?

Correct on all counts. As someone pointed out earlier, under male primogeniture a daughter can always be displaced by a son, a brother by a child, and they would hence be heir(ess)es presumptive – except for the hypothetical case where the heir apparent until then dies leaving only daughters, in which case the eldest daughter becomes heiress apparent, since she cannot be displaced while living. This has happened with noble titles that pass to heirs general (rather than heirs male), though never to the throne.

If, in the early 1930s, the then Prince of Wales had married a suitable woman (as he should have), and that woman had then given birth to a daughter, and the Prince of Wales had then died before King George V, that daughter would have been the heiress apparent. So it’s not hard to think of a circumstance where the British throne could have an heiress apparent.

What meaning of “should”? It seems to me that most people are quite relieved that he didn’t do what he “should” have done and, in so doing, showed himself the door.

Will investigate and respond later regarding the Duchy of Cornwall.

Regarding the Dukedom of Rothesay, etc. the Act regarding this was supposedly the one starting at the top-left corner of the main image appearing here. Unfortunately the image quality is somewhat poor, and the text is in abbreviated Latin, so I can’t confirm this. The text appears to be reproduced as text (i.e. not as an image) here (under the heading “Judicial proceeding: forfeiture of the Boyds”). With a bit of luck we can find a Latin speaker on here to give us a rough translation!

The image is from the first edition of The Acts of the Parliaments of Scotland, so the text is authoritative… the only question is whether the Act does what it’s said by Wikipedia to do! The “General Index” to The Acts of the Parliaments of Scotland seems to confirm at least in vague terms that it does:

Not much, but it’s all I have!

With a bit of luck someone around here has access to some relevant explanatory works regarding Scots law to flesh this out, although I’m not holding out much hope…

Well, if you’d asked King George and Queen Mary around 1930 what the Prince of Wales should be doing, and had got an honest answer, they’d probably have said the the prince should find a suitable woman, marry her, and produce an heir or two. It’s very easy in hindsight to say what would have been the best thing to happen.

The Records of the Parliaments of Scotland project itself provides a full translation.

The crucial passage is that the lands in question are ‘united, annexed and incorporated to the eldest prince of the kings of Scotland our successors in perpetuity’.

That this doesn’t actually create a dukedom of Rothesay isn’t news. But then there is no doubt that successive Scottish heirs apparent sat in the Scottish Parliament as such.

As for the Duke of Cornwall, the Duchy of Cornwall charter of 1337 unambiguously limits the title to the monarch’s eldest son, so there was no question of the future George III inheriting it in 1751. However, there was then some uncertainty as to whether the same was true of the dukedom of Rothesay and the government even considered legislating to resolve the point. But, in the end, it was simply assumed that it had also lapsed to the Crown. See Complete Peerage, sub. ‘Cornwall’, for more details on all these points than anyone could possibly want.

Actually, the Acts of the Parliaments of Scotland is filled with errors and was authoritative only the absence of any better edition. The RPS project was created specifically to provide that better edition.

By that definition, William is the second heir apparent to the British throne, since his position cannot be displaced.

Thank you! I was sure that they did translations of original sources from when they were unveiling the project (having lost my bookmarks since then :() but I couldn’t find a link from the page itself.

But it’s legally authoritative, no…?

It’s very frustrating trying to find your way into Scots law if you’re in England. Sadly the literature on “British” constitutional law is so anglocentric, it’s shocking.

After further investigation, I have confirmed that I was wrong, and that you were right.

The following are from Halsbury’s Laws of England, 4th edition (reissue), Vol. 12(1), “Crown and Royal Family”:

[QUOTE=para. 30 (extract)]
While the monarch’s eldest son is Heir Apparent, he is also Duke of Cornwall, by inheritance, in the peerage of England and is entitled to the duchy’s revenues. The duchy vests in the monarch’s eldest surviving son immediately he becomes Heir Apparent. Where the Heir Apparent dies leaving a son, the title and possessions of the duchy do not vest in the son, but revert to the Crown; for although the eldest son of the Heir Apparent becomes himself Heir Apparent on the death of his father, yet, not being the eldest son of the monarch, he is not within the limitations of the charter.
[/QUOTE]

According to the footnotes to the above, fuller details are given in The Prince’s Case, (1606) 8 Co. Rep. 1a. However, in that case Coke expresses the opinion that the charter confers the title on the first-born, rather than the eldest surviving, son of the monarch; the footnotes point out that this is not consistent with what had already happened in the case of either Henry VIII or Edward VI (nor is it consistent with what subsequently happened in the case of George V).

Also from Halsbury’s, citation as above, “Crown Property”:

[QUOTE=para. 320 (extract)]
On the death of the heir apparent without leaving issue the next surviving son of the monarch succeeds; but if the heir apparent leaves issue (who would in that case become heir apparent), the Duchy of Cornwall does not vest in that issue or in the next surviving son of the monarch, but reverts to the Crown under the general rule by which, in the absence of an eldest son and heir apparent, the duchy vests in the monarch.
The Duke of Cornwall has legal title vested in him on succession even if he is under 18. […] The Duchy is not as such a legal person […]. As the duke is an individual and not a corporation his actions are personal and can only bind a successor by virtue of statute.
[/QUOTE]

Incidentally, the Scottish Act discussed earlier appears to be missing from The Chronological Table of the Statutes. D’oh! Not the first howler I’ve found in it, but still.