A royal expert who was friends with the late Princess Diana is speaking out this week to say that she believes Meghan Markle and Prince Harry “won’t last” as a couple.

“She and Harry won’t last. Once she became the royal Duchess of Sussex, it was off with everyone’s head,” Lady Colin Campbell told Page Six, referring to Meghan. “Disconnected from reality, she lost it. She froths at the mouth when my name is mentioned. But nothing she can do because I made no legal mistakes. With all I stated about her — her background, how she learned about him — I am legally OK.”

“Since fallout from the Oprah piece, her name’s mud throughout the Commonwealth, even in the islands. This wrong-footed woman stated untruths,” Campbell added. “She couldn’t keep her mouth shut. Knowing some statements could not be massaged into reality, Harry went along. Not pleased, he knew they were not true. They were not already married three days before the big wedding. There’s a difference between fact and fiction. He knows the difference in a real ceremony. As did the Archbishop of Canterbury.”

Campbell then discussed what she believes will happen if Harry ever wants to make a comeback in an official capacity.

“No matter how disagreeable, the Crown handles situations,” she explained. “hey’ll wait until the situation crystallizes. For now dignity and politesse rule the situation. She’s picked America and a communal property state and has two children. She’s got him. Difficult for him to get out. He’s entrapped.

“Returning, London would act polite. Be received politely,” Campbell continued. “Treated with respect. The Establishment, however, will treat him as a pariah.”

This is far from the first time that Campbell has spoken out against Meghan. Last summer, she compared her to Lady Macbeth, the villainess in the legendary play by William Shakespeare.

“Meghan’s influence is very reminiscent of Lady Macbeth,” Campbell told The Sun back in August. “It’s so sad because I remember Harry growing up and he was great with my kids. To gain a toehold over Harry she appears to have played to his weaknesses, just as Katherine has played to William’s strengths.”

“Meghan shares a lot of Harry’s weaknesses. He is hyper-emotional, over-the-top, rushes where wise people don’t and is extremely self-important,” she added. “The way she has acted is ­completely unacceptable in the Royal Family. Even Diana knew how to be a princess and when to toe the line. Meghan appears, to me, very good at talking the talk and not walking the walk. She is leading Harry down a path he will struggle to find his way back from. I fear for them.”