According to a royal historian, Prince Charles is "unfit to be king" because his "rackety past" could harm him and the monarchy.

Since the beginning of the lockdown period, most royal family news tackled how Prince Charles could finally take over the throne, especially with Queen Elizabeth II taking quarantine indefinitely with Prince Philip.

However, most of the reports also pointed out how he could destroy the monarchy once he becomes king.

In the ITV documentary "Inside the Crown: Secrets of the Royals," royal expert Piers Brendon explained how Prince Charles' past could ruin The Firm.

"He has got a lot of uncomfortable baggage that the Queen never had. She emerged absolutely pristine onto the throne," Brendon said before adding that the Prince of Wales had a very "rackety past."

According to the royal expert, this could lead him to divide opinions rather than uniting it -- something that a monarch should never do.

This came after royal expert Dickie Arbiter also said in the same documentary that Prince Charles will need to "constitutionally keep his mouth shut" once he takes over since he has broken the royal household's neutrality numerous times already.

Arbiter said, "He has written letters to Ministers asking the sort of question that we would want an answer to. He won't be able to do that when he becomes King."

For instance, Prince Charles received major backlash in the early 2000s after he became too political when he attempted to stop the publication of the "black spider memos." It is reportedly a controversial collection of communications he directed to the ministers and Cabinet members through the years.

However, the Clarence House tried to defend him and said that Prince Charles was just concerned about the wider world.

"The letters published by the Government show the Prince of Wales expressing concern about issues that he has raised in public like affordable rural housing, the quality of hospital food, the preservation and regeneration of historic buildings, an integrated approach to healthcare, climate change, and others," the Clarence House said in 2015.

What Exactly Happened In The Past?

Aside from his "too political" side, Prince Charles also went through a lot as a child.

Prince Charles was only three years old when he became heir apparent. As he grew up, he slowly realized that he would one day be king. Unfortunately, there have already been doubts about his fitness for the said future role since he was young.

Because he was too soft, the Prince of Wales caused disappointment to his parents. Queen Elizabeth II and Prince Philip then pushed him to undergo an "extensive training" to become the best king to succeed Her Majesty.

To resolve his issues, Prince Philip sent him to Gordonstoun -- a Spartan boarding school -- where he experienced hard times both from his schoolmates and father.

According to Historian Robert Lacey, Prince Philip made the choice because he had genuine plans, and he believed that making him stay in the dormitory would build Prince Charles more and would help him grow on his own.

In the end, the Prince of Wales found the challenges in the past as something "uplifting."

READ MORE: King's Pain: Prince Charles MUST SACRIFICE Before Ruling Monarchy