The Duchess of Sussex upset the Duchess of Cambridge by saying she must have “baby brain” in the run up to the royal wedding in 2018.

In his bombshell autobiography Spare, the Duke of Sussex said his wife made the comment during a phone call about wedding rehearsals, according to The Sun’s translation of a Spanish copy of the book.

Kate, who suffered from hyperemesis gravidarum, a condition caused by hormone imbalance, during all three pregnancies, had recently given birth to Louis.

Harry also claims in his book that during the fallout Kate admitted to making Meghan cry.

He claimed that his wife apologised to Kate, saying that is how she speaks to her friends.

But the Duke of Cambridge then “pointed a finger” at Meghan, saying: “Well, it’s rude, Meghan.

“These things are not done here.”

Meghan then apparently responded by saying: “If you don’t mind, keep your finger out of my face.”

It comes after reports emerged at the time that Meghan had made Kate cry over flower girl dresses in the lead up to the wedding.

During an interview with Oprah Winfrey last year, Meghan claimed the “reverse happened” and it was Kate who had made her cry.

The duke also writes that they were angry Kate and William’s press team had not corrected the media after the incident.

He said Kate was flustered and William was evasive, adding that the Cambridges would not issue a statement to avoid putting the Queen in a difficult position.

Other revelations emerging on Thursday include Harry’s claims that the brothers “begged” their father not to marry Camilla and that a campaign was launched for Charles to marry her.

The Guardian, which said it was able to obtain a copy of Spare despite the tight pre-launch security, reported that Harry claims he was physically attacked by William and knocked to the floor during a furious confrontation over the Duchess of Sussex.

Harry writes: “(William) called me another name, then came at me. It all happened so fast. So very fast.

“He grabbed me by the collar, ripping my necklace, and he knocked me to the floor.

“I landed on the dog’s bowl, which cracked under my back, the pieces cutting into me.

“I lay there for a moment, dazed, then got to my feet and told him to get out.”

Other reported revelations include how the brothers call each other “Willy” and “Harold” and that Charles pleaded with his sons during a tense meeting after the Duke of Edinburgh’s funeral: “Please, boys. Don’t make my final years a misery.”

The book comes just weeks after Harry and Meghan’s bombshell Netflix documentary in which Harry said he was left terrified when William screamed and shouted at him at a tense Sandringham summit in 2020.