Similar to the person who knows someone in their security team who confirmed it to be true, I can also 100% vouch for it being true
Won’t say the name of my company but I work for a big media organisation associated within the news
In 2019 a very senior colleague was sent a message from the liaison at the palace asking us not to report on the affair with Rose, instead they could give us other info in exchange for the company’s avoidance on the matter.
At the time the French press had run the story openly, quoting sources, but the palace had threatened the UK press with legal action if they ran it saying it “was against Prince William’s human rights” to have his life written about in this way. The UK press felt they couldn’t name the affair explicitly, so instead began writing about a “falling out” between Kate and her neighbour Rose.
The fact of the matter is that the French press incl Vanity fair have named this woman - IN PRINT - and still the royals haven’t sued them for defamation, nor has Rose sued them for defamation. Why would they not do that if it weren’t true?
This was also supposed to the biggest argument between Harry and William, his finding out about the affair.
Supporting link here Coverage of French press