It seems as if Ms Markle has won the first round of her case against 'The Mail on Sunday' newspaper (Associated Newspapers Limited), for having published that private letter to her father.
In my personal opinion, the Judge (Mr Justice Warby) was absolutely right. There is no question that there was misuse of private information, and an infringement of copyright; copyright always belongs to the writer of a letter (and/or other personal work). Appropriation of such copyright is a serious offence.
I am no fan of Ms Markle, but the law is rightly on her side. Her frustration must have been 'off the scale'.
Readers may remember that I, myself, have been the victim of blatant theft of copyright. I was advised at the time that there wasn't a court in the world that wouldn't find in my favour as far as damages were concerned. I was also wisely advised that it was probably 'more gentlemanly' not to damage the offender financially, or upset neighbourly relationships, so I reluctantly allowed him to stay away from court.
As with The Mail on Sunday, lessons must be learned; although I expect that any damages Ms Markle can expect, will be far in excess of what mine might have been.