Queen Elizabeth II
Queen Elizabeth changing one law about marriages would've changed the course of history for Prince Charles and Princess Diana. Pictured: The Queen smiles as she arrives before the Opening of the Flanders' Fields Memorial Garden at Wellington Barracks on November 6, 2014 in London, England. Getty Images/Stefan Wermuth - WPA Pool

Queen Elizabeth could’ve stopped Prince Charles from marrying Princess Diana with a single law change.

In the book “Charles, Prince of Wales,” author Anthony Holden said that the Queen wanted to abolish the Royal Marriages Act in favor of Prince Charles so that her eldest son could have more freedom with his marriage plans.

If Her Majesty pushed through with this law change, Prince Charles would’ve been allowed to wed Camilla Parker Bowles before even getting engaged to Princess Diana. Camilla’s status as a divorced woman wouldn’t have been a problem as well if the monarch changed the law.

The book, which was published in 1979, claimed that it is still possible that while the Queen is still alive, royal fans may see the repeal of both laws restricting royal choice.

“The Queen has it in mind to persuade a prime minister to do away with the Royal Marriages Act. The Royal Marriages Act has outlived its purpose,” Holden wrote.

Matthew Kirkham, a journalist for Express, said that the act has also proved to be unrealistic, especially during the latter part of the 20th century by Princess Margaret’s divorce, and the divorce and remarriage of the Queen’s cousin, Earl of Harewood.

Last year, Prince Harry also announced his plans to wed Meghan Markle, a divorced American actress. But it was only on March 15 that the couple’s engagement became official. They tied the knot at St. George’s Chapel in Windsor Castle on May 19.

Her Majesty also released a statement giving her formal consent for the Duke and Duchess of Sussex to tie the knot. Without the consent, Prince Harry and Markle’s wedding would have been unrecognized under the UK laws.

The 1772 Royal Marriages Act states that “Every marriage, or matrimonial contract, of any such descendant, without such consent first had and obtained, shall be null and void to all intents and purposes whatsoever.”

This rule was updated in 2013 after the passing of the Succession to the Crown Act. The act states that only the first six Royals in line to the throne requires the Queen’s permission to validate their marriages.