This still seems rather flimsy though. I mean this still feels like it falls into the "interesting to the public" but not "in the public interest"
If Meghan was writing to government officials, even in a personal capacity, that to me is "in the public interest" but, taking the idea that she authorised her friends to share the letter at face value, a tit for tat with her dad is still a personal matter that ultimately has no bearing on the public condition.
I mean again, good lawyers are experts at winning on the thinnest of margins but I imagine the Sussex lawyers have fairly robust defenses too.
Yes, that's an argument Meghan's lawyer's will likely make - publishing a private letter without permission was not in the "public interest."