According to a royal journalist, Meghan Markle is facing a conspiracy from the so-called “men in grey” at Buckingham Palace who are “planning her downfall.”

Insiders at the Palace believe the Duchess of Sussex, 37, is a “threat to the throne,” according to Anna Pasternak, author of a biography of Princess Diana.

She is currently working on a book on American divorcee Wallis Simpson, whom she thinks Meghan reflects. The monarchy was shaken by Ms Simpson’s affair with then-King Edward VIII, which led to his abdication and a shift in the royal family’s fortunes. In 1937, when the pair married, Queen Elizabeth II’s father succeeded him as King.

Meghan, has “rejuvenated the spirit” of the American divorcee who upended the monarchy, according to Pasternak.

She told the Sunday Express’ S Magazine: “Meghan is like a grenade that’s been thrown into this archaic system and there are explosions already going on which I think will continue”

“In a sense Meghan has rejuvenated the spirit of Wallis and I hope people take the view of her as a kind, witty, loyal and dignified person who unfairly became the most vilified woman in the world.”

Princess Diana had previously discussed the “men in grey” during her marriage to Prince Charles.

Ms. Paternack went on to say: “I worry for Meghan and Harry.

“He’s the people’s prince as Edward was the people’s king.

“I fear if Meghan and Harry’s star rises too high that will be perceived as the courtiers Princess Diana called men in grey as a threat to the heir.

“She cannot set the agenda, she has to toe the line, and support the monarch and heir. I don’t think she realises that.”

Meanwhile, it was revealed that Meghan and Harry paid a surprise visit to her mother Doria in Los Angeles a few months ago.

While the exact date of the trip is unknown, a neighbor told The Sun that Meghan “will always come back to Doria, this will always be her home.”

“They are forever in touch, and Meghan has been here to stay on more than one occasion since going public with Harry.

“I even saw him here once, but it’s not my place to say any more.”

Samantha, the Duchess of Sussex’s half-sister, recently accused her of living a life of excessive luxury.