“No one’s saying it’s responsible for all the trouble, but deliberately calling someone by a name they don’t like is just bloody rude,” said the friend.

“If Harry and Meghan were serious about healing their issue, a good first step would be to call her Catherine.”

The apparent reluctance on Harry and Meghan’s part to call the Princess of Wales by her preferred name was “an entirely unnecessary and deliberate irritation” and may have contributed to William and Kate’s refusal to respond to Harry and Meghan’s expressions of sympathy after her cancer diagnosis.

The name request sent by Kate came in 2008 – two years before William ultimately popped the question.

Prince Harry also previously wrote in his bombshell memoir Spare that the now-King “asked his daughter-in-law to change the spelling of her first name”.

The former working royal claimed that his father wanted his sister-in-law to change her name spelling from a C to a K.

The Duke of Sussex wrote that he spoke to his brother at the time about their father’s suggestion: “I turned to Willy, gave him a look that said: ‘You listening to this?’ His face was blank.”

Kensington Palace has been approached for comment.