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Forget Meghan Markle’s alleged feud with Kate Middleton, or her reported Bridezilla demands before her wedding.

The real royal scandal may have nothing to do with the American Duchess of Sussex — but with a story about Kate and Prince William. Until this week, mainstream publications in both the U.K. and the United States had been reluctant to pick up on the story.

It involves the unsubstantiated but persistent and “sensational rumor that has electrified British high society for almost a year,” the Daily Beast reported Tuesday.

The rumor is that William may have become too friendly — or even had an affair — with an aristocratic neighbor while his wife was pregnant with their third child, the Daily Beast added.

Both the Daily Beast and Slate, also reporting on the rumor this week, said it has gained steamed in part because In Touch Weekly, a mainstream U.S. gossip magazine, ran a cover story in the past week with the headline “WILLIAM CHEATS ON KATE — with her friend!”

“The publication of the rumors by In Touch will doubtless be a matter of grave concern behind palace walls, as it represents the first serious breaching of a self-imposed wall of silence on the alleged affair by the mainstream media,” Daily Beast writers Lachlan Cartwright and Tom Sykes said.

The Daily Beast and Slate also reported that royal lawyers have sent a cease-and-desist letter to at least one U.K. publication that reported on the rumor.

“It is not entirely surprising that the palace should be alarmed at a story which invites comparisons to Prince Charles’ adulterous relationship with Camilla Parker Bowles while he was married to Diana,” the Daily Beast said.

According to the Daily Beast, Slate and Lainey Gossip, the rumor first made its way into the U.K. press in late March, with a report in The Sun about how William and Kate had begun spending more time at their estate in rural Norfolk and become part of “a country-posh” set known as the “turnip toffs.”

In that circle, The Sun reported, the Duchess of Cambridge had become best friends with Rose Cholmondeley, a former model who also is in her mid-30s, who also has young children and who is married to David Rock­savage, a man 23 years her senior. Rocksavage also is known as the Marquess of Cholmondeley and comes from an old aristocratic family.

But Kate, for some reason, told William that Rose needs to be “phased out” as one of the couple’s close friends. A source told The Sun: “It is well known that Kate and Rose have had a terrible falling out. They used to be close but that is not the case any more.”

That was it for the Sun story — that Kate had a falling out with a friend, without saying why. The story might have died there because, as Slate’s Ruth Graham wrote, who cares about a “tiff between two toffs?”

But two days later, the Daily Mail’s royal correspondent Richard Kay went to great lengths to rebut The Sun report. Kay quoted royal sources as saying that the two couples were never that close, though they are apparently close enough to laugh off The Sun report.

Kay decried the way the Duchess of Cambridge has become a victim of aristocratic party gossip, while launching into a defense of William as an upstanding man, husband, father and future king of England.

Kay said William was “determined to act as extraordinary rumors engulfed his family, threatening to disrupt their domestic tranquillity.”

Kay furthermore said that William and the marquess were considering legal action.

“For the royals, dealing with such rumours has long been a delicate conundrum,” Kay wrote. “Ignore them and the risk is that they will be amplified, but by speaking out there is danger of somehow giving legitimacy to what, as we shall see, is almost certainly nothing more than scuttlebutt.”

But the idea that anyone would take legal action over The Sun report prompted Lainey, of Lainey Gossip, to ask: “If it’s just a story about two women not getting along anymore, like how Kate and Meghan allegedly haven’t been getting along, why bother with the lawyers?”

Meanwhile, a certain cheeky member of the British media tweeted about the rumor, saying “Everyone knows about the affair, darling,” Slate reported. The reporter quickly deleted his tweet. Still, he was suggesting that a major scandal “was about to blow,” Lainey Gossip said.

Slate contributor Nicole Cliffe also took to Twitter to publish a lengthy thread on the rumor’s history. Cliffe said William and Kate “flipped out” over the initial Sun report about her supposed falling out with Rose Cholmondeley.

Cliffe also raised the question of whether the supposed feud between Kate and Meghan was really a feud between Harry and William over the older brother’s alleged affair and betrayal of his wife and children.

Cliffe wrote: “Wills would absolutely have told Harry about the affair, bc of how those two are, and I think that Harry was like ‘this is exactly what ruined our childhoods, this is pulling some Dad (expletive), you have three small children, what the (expletive)?”

Then came the In Touch story, which quoted a source as saying Kate “immediately confronted” William when she heard about the rumored affair, according to the Daily Beast. William “just laughed it off saying there was nothing to it,” In Touch reported.

In Touch added that William and Kate do not intend to break up, but said the scandal “has rocked the palace and their marriage.”

The Daily Beast said Kensington Palace would not comment on the record about the In Touch story, but royal aides privately said that the story is “totally wrong and false.”

The aides also questioned In Touch’s credibility. That view was seconded by Lainey, who wrote the publication “probably gets one thing right every six months.”

“But reliable or not, they may have just given life to a story that the House of Cambridge was hoping would go away,” Lainey added.