EXCLUSIVE: Prince William 'Fights Brother Harry's Plans for Princess Diana Film'

Prince William is pushing back on Prince Harry's plans to produce a movie about their late mother, Princess Diana – and vowing to banish his brother and his high-heeled wife, Duchess Meghan Markle, from the monarchy once and for all, RadarOnline.com can reveal.

The project, set to be released in 2027, reportedly will commemorate the 30th anniversary of Diana's tragic 1997 death, but royal experts say the 44-year-old heir to the throne believes the cash-strapped Sussexes are simply seeing dollar signs and exploiting the royal family for cash.

"This brings back memories for William of his brother's memoir, Spare," an insider told RadarOnline.com, referring to Harry's bridge-burning 2023 autobiography. "William fears the movie will reveal even more secrets about the royal family" – although a palace source denied the story.

The ever-widening royal rift leaves cancer-stricken King Charles caught between his two warring sons – with William willing to do anything to protect the monarchy.

Insiders say William is livid that 77-year-old Charles welcomed Harry and his family back to the U.K. in August.

"When his father dies, William plans to banish Harry forever," the insider said. "Harry will become persona non grata in the U.K."

Many believe Harry drove the final nail into his coffin shortly after news spread about his movie project – starring his former Suits star wife, no less.

"To William, it's crossing a line that can't be uncrossed," another insider said.

What's more, insiders predict the future king will become further enraged if the Sussexes bring their movie project to their business partners at Netflix – given the controversial way the streamer's hit series The Crown portrayed Britain's royal family.

But sources said Harry is convinced it's his "duty" to memorialize his mom and believes Diana's story has yet to be told properly.

Royal expert Hilary Fordwich said Charles and Queen Camilla, 79, are dreading the project because it will only remind the public of their scandalous affair.

"Neither the king nor Camilla has any interest in there being a lot of focus on Diana," Fordwich told RadarOnline.com. "King Charles can't be relishing the thought of an entire year dedicated to Princess Diana's death."

In an apparent bodycheck to his son, Charles recently blindsided Sussexes by publicly clarifying in a letter to government officials that the pair remain non-working royals – unchanged since Harry, 42, and Meghan, 45, ditched their duties in 2020 to live in California.

A Sussex spokesperson said of the letter: "We were a little surprised not to have been told about this in advance."

Shortly after Charles' letter was released, Ugandan General Muhoozi Kainerugaba abruptly announced plans to pull out of Harry's 2027 Invictus Games for wounded veterans and service personnel in Birmingham, saying he didn't want Uganda's participation to be "construed as being opposed" to the king, who "we deeply revere."