Oh, you seem new to royal watching. I take it you’ve never seen The Queen, for example. Perhaps you should watch it so you can have a small glimpse of what goes on beyond the Meghan Markle fandom.
Charles publicly dated Camilla FOR YEARS before they became married. Charles and Camilla’s first public appearance was in 1999. The didn’t get married until 2005. That’s SIX YEARS between their first public appearance and marriage. And EIGHT YEARS after the death of Diana.
And as for whether or not the British royal family–including Charles–cares about public opinion, they do. Obviously you have not noticed that the title Camilla uses is Duchess of Cornwall instead of Princess of Wales. Camilla has every right to use the Princess of Wales title; however, she doesn’t in deference to public opinion regarding Diana.
