Charles Spencer has revealed exactly what Princess Diana thought of Donald Trump - and it's not pretty.
The former US President recently made another outlandish brag about the former Princess of Wales, who he once lewdly claimed he could have had sex with.
Trump has been boasting about revealing 150 letters in a new book which were sent to him by celebrities, world leaders and members of the Royal Family.
"I knew them all – and every one of them kissed my a**, and now I only have half of them kissing my a**," he claimed.
Now Spencer has slammed Trump, accused him of using Diana to "sell some real estate, and humiliatingly divulged what his sister really thought about him.
Charles tweeted: "Surprised to hear that Donald Trump is apparently claiming that my late sister Diana wanted to 'kiss his a***', since the one time she mentioned him to me - when he was using her good name to sell some real estate in New York - she clearly viewed him as worse than an anal fissure."
For those who are unaware of exactly what that insult means, here is the medical definition.
According to the NHS : "An anal fissure is a tear or open sore (ulcer) that develops in the lining of the large intestine, near the anus.
"Anal fissures are most commonly caused by damage to the lining of the anus or anal canal, the last part of the large intestine.
"Most cases occur in people who have constipation, when a particularly hard or large poo tears the lining of the anal canal."
While Spencer stopped people from replying to his tweet, many quote tweeted his statement with their responses.
One furious commenter wrote: "Trump's audacity to mention #PrincessDiana in the same sentence as himself makes me sick not to mention his fantasy that Diana would ever kiss his ... Trump you can dream all you want but stop making false claims about our dear Diana. Lies to make yourself relevant."
"She's taking him down from beyond the grave. that's real power," added another.
Addressing Trump's political rival, Ron DeSantis, a third said: "I think DeSantis has a slogan for his presidential campaign: "Donald Trump: Certifiably worse than a royal anal fissure."
It's not the first time that Trump has made questionable lewd remarks about Princess Diana.
In a shocking 1997 interview with Howard Stern, he brazenly claimed he could have had sex with the former Princess of Wales - but only would have done so if she passed an HIV test first.
Trump was asked: "Why do people think it’s egotistical of you to say you could've gotten with Lady Di? You could've gotten her, right? You could've nailed her?"
"I think I could have," Trump replied, before adding that he would have made her take an HIV test.
The duo then acted out a bizarre skit in which Trump pretended to offer Diana a "little check-up" in his Lexus, before he gushed over her "beautiful skin".
"She was actually really beautiful. I thought she was supermodel beautiful," Trump said. "She had times when she didn’t look great and she had times when she looked better than anyone in the world."
That same year, he also leered over Diana in his book, The Art of the Comeback.
"I only have one regret in the women department, that I never had the opportunity to court Lady Diana Spencer," he said.
It appears the feeling was not mutual, as Diana's friend, Selina Scott, claimed the shameless self-promoter gave the princess "the creeps".
She said: "He bombarded Diana with massive bouquets of flowers. She became increasingly concerned."
Christopher Andersen's book, The King: The Life of Charles III, detailed how Trump had 'aggressively pursued' Diana following her divorce from then Prince Charles in 1996.
It was also claimed in the book that Diana actually 'rebuffed' the advances of Trump.
Trump has also made outlandish claims about other members of the Royal Family.
In April last year, the former The Apprentice star claimed the Queen and Camilla were competing with each other for his attention at a royal banquet.
Speaking to Piers Morgan, he recalled: "She [Camilla] was on my right, the Queen was on my left, and I said 'Queen, I really have to talk to Camilla for a little while too'. We couldn't break apart.
"[Camilla] was funny, she was smart, she was quick, she was great. I like her too. I like Charles."
Trump also suggested the Queen had "never had such a good time" than when he was sitting next to him at the state banquet.
He has given his backing to the new King, claiming that he has "got a great way about him" while he was also a fan of Camilla saying she was "absolutely lovely".
Speaking on GB News in October, Trump said: "I know [Charles] very well, quite well. And I spent a lot of time when I was over there as President with him. And with his wife (who) was absolutely lovely, by the way, and we had a good time together.
"And I, you know, so I'm a little prejudiced when I say it, but, you know, he had a strong view on things.
"Probably difficult when you're the King you want to have 100% of the people love you like the Queen did. The Queen had - everybody loved her, right? She didn't have that kind of an agenda.
"And yet, you know, she was a very strong woman. I got to know her too. She was a very strong woman, a great woman. I think Charles is going to do very well. I think he's got a great way about him."
