A 4-year-old Prince William told his nanny he would punish her when he becomes king, a new royal book says

• Prince William reportedly used to tell his nanny that he would "punish" her when he becomes king.
• According to Tina Brown's new book, "The Palace Papers," William made the claim at the age of four.

The Duke of Cambridge went through a rebellious stage as a child, which involved telling his nanny he would punish her when he becomes king, according to a new royal book.

In "The Palace Papers," published on Tuesday, author Tina Brown writes that Prince William was aware of his status as a future monarch from a young age.

"By the time he was four, he had the unattractive habit of yapping at his nanny, Barbara Banes, 'No one tells me what to do! When I am king I will have you punished,'" Brown wrote.

The author said she spoke with more than 120 people for the book, many of whom she described as being "intimately involved" with the senior royals. One of those people, who spoke anonymously to Brown and is described as a former staff member of Princess Diana, recalled an alleged incident with William when he was eight years old.

The former employee said that during a plane journey back from William's first formal trip to Wales, he "reached over with his fork and speared a hard-boiled egg" from their plate.

"It was as if the boy had said, 'I'm going to be king. You're not and I'm going to have what I like off your plate... What are you going to do about it?'" Brown wrote.

The former employee told Brown that when Princess Diana scolded William, he went into a temper tantrum.

Kensington Palace declined to comment when contacted by Insider.