But in his memoir Spare, published in the UK on January 10 by Penguin Random House, the Duke of Sussex refers directly to this hearsay.
He wrote: “The joke was damn funny in light of the rumour going around at the time that my real father was one of my mother’s ex-lovers: Major James Hewitt.
“One cause of the rumour was Major Hewitt’s red hair, but another was sadism.
“Tabloid readers loved the idea that Prince Charles’s youngest son was not Prince Charles’s son. They never got tired of that ‘joke’, for some reason.”
In the book Harry wonders whether the rumours were designed to make him a “laughing stock”.
He says people still believed the rumours despite Diana never meeting Major Hewitt until after he was born.
He also claims that journalists attempted to hunt for his DNA profile to verify the rumours and sent his mother into hiding, prompting Harry to believe they would come after him.
Harry adds that over the years, the versions of the rumours were changed and published by media publications and that reports about Charles reassuring Harry that Major Hewitt was not his father are made up.
Spare also contains several other shocking revelations from Harry, including claims that his brother Prince William attacked him during a row over his wife Meghan Markle.
It was also reported that King Charles begged his sons not to fight with one another at Prince Phillip’s funeral back in April 2021.
The King reportedly said he wanted to avoid the despair in his “final” years and at one point stood between the two of the warring brothers.
Kensington Palace and Buckingham Palace have declined to comment on the leaked claims from Harry’s book.