Princess Kate's lip gloss or Meghan's envy: What broke the royal bond

Prince William and Prince Harry's once-unbreakable bond allegedly shattered after Meghan Markle entered the Duke of Sussex's life.

However, the fight which believes to have started with a small argument caused a big mess.

Even Harry penned about Princess Kate, whom she once regarded his beloved sister, alleging she was difficult in the run-up to his wedding.

It was Harry's portrayal of the Princess of Wales as "cold" that insiders say proved unforgivable for William, leaving the future king convinced he could never again fully trust his younger sibling.

In short, Harry's pen proves to be poision for William as it spewed venomous words that forced William to draw a line.

The Duke claimed Kate was frosty to Meghan when she asked to borrow some lip gloss.

He also included a passage where his wife asked an allegedly frosty Princess for a touch of her lip gloss, which did not go over well.

"Meg asked to borrow Kate's lip gloss. An American thing. Meg apologized. But Kate, taken aback, went into her handbag and reluctantly pulled out a small tube. Meg squeezed some onto her finger and applied it to her lips. Kate grimaced," Harry wrote about his once beloved sister-in-law.

William even decided he was 'done' with Harry after what he wrote about Kate Middleton in 'Spare,' a source claimed.

"Was there anything that just got to William so much, that broke his heart so much that he just couldn't get over it?" a panelist asked former People and Us Weekly Editor in Chief Dan Wakeford during a recent episode of The Royals Uncensored podcast.

Wakeford's contacts run deep within both the palace and the Sussex camp, and he was quick with an answer.

"I mean, the betrayal of talking about the family, but one in particular. It was talking about Kate and portraying her as cold through a series of anecdotes in Spare is something that William really could not get over, and is the thing that makes him realize, 'I am done. I don't want to pursue this. I'm done with this drama,'" the longtime journalist explained.

"He could deal with the criticisms of himself," Wakefored revealed, "But criticising Kate really was the straw that broke the camel's back here."

Harry included a number of his "truths" in the book, claiming the Princess of Wales dressed down his future bride when Meghan reportedly told her it was okay that she was being forgetful, chalked it up to "baby brain." 

Harry also accused his sister-in-law of leaving "sobbing" on the floor after insisting that the bridesmaids' dresses needed to be completely remade days before their wedding.