Prince Harry
Prince HarryReuters

A new book allegedly contains details of William and Kate’s inappropriate reaction to Prince Harry’s offensive Nazi costume worn at a party in 2005.

According to leaked excerpts from Harry’s soon to be released book, Spare, William and Kate “howled with laughter” at the prince’s Nazi uniform, the UK Jewish News reported.

The Nazi uniform was worn by Harry at a party in early 2005, earning him widespread condemnation.

Prince Harry claims in the book that William and Kate encouraged him in a phone conversation to wear the Nazi uniform when he asked them if he should chose it or instead go to the costume party as a pilot.

Writing about the conversation in his book, Harry alleges that he even tried on the uniform for his brother and sister-in law.

“I phoned Willy and Kate, asked what they thought. Nazi uniform, they said,” Harry recalls, according to an excerpt obtained by PageSix. “They both howled. Worse than Willy’s leotard outfit! Way more ridiculous! Which, again, was the point.”

The then-20-year-old prince was widely denounced when a photo of him wearing the Nazi uniform was published on the front page of a newspaper.

He recently said in his Netflix documentary that the incident “was probably one of the biggest mistakes of my life.”