This column from 1976 contains an inaccuracy or two.
It is true that rarely has England’s heir apparent succeeded to the throne without having previously been created Prince of Wales (other exceptions according to my source are Henry VI, 1422; Edward VI, 1547; and perhaps Charles II, 1649). But there have been numerous ``British rulers’’ (not even counting kings of Scotland before 1603!) who never were heirs apparent, and thus could not be PoW - including the present queen and her father.
Because Anne wanted her children to live as `normally’ as reasonably possible.
That had to wait for the death of the previous Princess Royal (Elizabeth’s aunt Mary) in 1965. I don’t know when it was done, but I certainly have heard Anne referred to by that style.
But I looked it up in the first place to see whether an inaccuracy in the book, supplied by a Teemer, is preserved on the website (happily it is not): the claim that if a PoW dies vita patris the crown goes to his brother rather than his child; in other words, that the late king’s sons all come before any of his grandsons. The nearest I can find to an example of this `rule’ is the succession in 1199 of John (fourth son of Henry II) rather than his nephew Arthur of Brittany (son of Henry’s third son Geoffrey, who had died in a tournament in 1186; Arthur was murdered in 1203).
In 1760 the crown went to George III, son of the dead first son of George II, rather than to the latter’s surviving son William Augustus duke of Cumberland. In 1837 it passed to Victoria, only child of George III’s fourth son (the first three having left no legitimate children), rather than to George’s fifth son Ernest Augustus duke of Cumberland & Teviotdale - though Ernest did get the crown of Hanover, where strictly male succession was the rule.