I've been corrected by Hilary, who points out that Camilla Parker Bowles is not styled a "princess"; she is merely the Duchess of Corwall. Indeed. I suppose I would know that if I read supermarket tabloids or watched more TV. (I'm certainly not suggesting that's where Hilary gets her information. She is, after all, a subject of the British monarchy in some vague sense).
For my part, I suppose with a little more thought and research, I wouldn't have referred to "Prince Charles," either, as I suppose the proper way St. James would make any annoucement is simply to refer to the "Prince of Wales." What do I know?
And for Hilary, I wonder if it's safe for her to refer to the Windsors and their concubines as "usurpers"? It's certainly safe for a Yank like me to do so. But somone actually living in the Dominions claimed by the usurper can get herself hanged, drawn and quartered, can't she?