They are friends no more...

Kate Middleton's 'Tatler' Lawsuit Targets A Former Friend Who Betrayed Her, Report Says

Kate Middleton and Kensington Palace's legal action against Tatler takes aim at the magazine's editor, Richard Dennen. It's now been revealed that he and the Duchess were once friends, and reports say Kate feels "betrayed" by his actions. Get the details below.

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Reports say that Kate Middleton was betrayed by former friend Richard Dennen in the publication of Tatler magazine's cover and article "Catherine the Great."

Dennen, the magazine's editor-in-chief, was friends with Kate while the pair studied art history at the University of St. Andrews in Scotland.

As a result of the friendship, the article caught Kate off guard. "Kate feels betrayed, as Richard had been a friend from the St Andrews set. She never saw this coming," a source told The Sun UK.

The report added that the pair had even vacationed together while William and Kate had separated.

Kate Middleton takes legal action against Tatler and Richard Dennen

Earlier this week, the Duke and Duchess of Cambridge took legal action against Tatler over "false misrepresentations" in the article.

Among many accusations, the profile said the Duchess resents the larger workload brought upon her by Harry and Meghan's royal exit, which has left her feeling "exhausted and trapped."

Kensington Palace has sought to remove the piece from the Internet, calling its allegations — which also touch on everything from Kate's weight to her children and even her mom, Carole — a "string of lies" and sexist.

But Dennen, Kate's one-time friend, has reportedly stood behind the reporting and sources in the article, which was written by journalist Anna Pasternak.

Tatler's response to the claim reads: "Kensington Palace knew we were running the 'Catherine the Great' cover months ago and we asked them to work together on it. The fact they are denying they ever knew is categorically false."

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The source further told The Sun: "There are a lot of unanswered questions, particularly who said these things to Tatler because [Kate's] real friends would never talk that way about her."

In the time that's passed since the announcement of legal action, the source added, "Kate remains hurt and upset by the article. It was very unpleasant."

The ongoing case is an atypical one in that it's seen the royal family directly acknowledge the press. And it appears that the Dennen connection adds a very personal element to Kate's case against Tatler. Meghan Markle earlier initiated her own lawsuit against The Mail on Sunday in a similar move.