Prince William was doubtful of Prince Harry's relationship with Meghan Markle from the start and he made this perfectly clear to his brother.

Excerpts from Christopher Andersen's book "Brothers And Wives: Inside The Private Lives of William, Kate, Harry And Meghan," retrieved by Page Six revealed that the Duke of Cambridge urged his sibling to take things slowly in his relationship with the then-actress. He reportedly asked him "Why rush things?" when the younger royal told him about his plans to propose in September 2017.

It is said that Prince William's comment had infuriated Prince Harry and he lashed out at his brother saying, "Who the hell do you think you are?"

A palace insider likewise told the author that the once-close bond between siblings was shattered when Meghan Markle entered the picture. The Duke of Cambridge was said to be charmed at first when he learned of her virtues from his brother before they were introduced. But he soon harboured doubts.

Aside from Prince William, others close to the Duke of Sussex also became concerned about his whirlwind romance. They were especially worried about his reputation especially since he only met the former "Suits" star on a "blind date" and that she was a divorcee.

Andersen claimed that Prince William even enlisted the help of their uncle, Princess Diana's brother Earl Spencer, for help in urging his sibling to slow down. This allegedly only made "matters far worse" and infuriated Prince Harry to learn that "his brother was actively seeking to have others interfere in his personal affairs." He soon became "angry" with anyone who is against Meghan Markle.

The royal family was also "alarmed" by revelations made by the former actress' estranged family, including from her father Thomas Markle Sr. and half-siblings Thomas Jr. and Samantha. They had warned the 37-year old from marrying their sister as they alleged that she would only bring shame to the royal family.

Andersen claimed the drama mortified Prince Harry and Meghan Markle. It horrified Prince William who later confided with a friend that he does "not know what to believe" anymore. He also told Prince Charles that Prince Harry's "obsession" with Meghan Markle was unlike anything he had ever seen. He then went on to admit to their father, "it feels like I have lost my best friend."

Meghan Markle, Prince Harry and Prince William
Prince Harry last year revealed that he had grown apart from his older brother William Photo: AFP / Tolga AKMEN