Prince Harry was advised to see a therapist by his concerned ex-girlfriend after venting about his older brother William and 'pouring out resentments' towards his father King Charles, according to a new bombshell book.

Actress and model Cressida Bonas, who dated Harry from 2012 until 2014, was so worried about the duke that she persuaded him to go talk it out with a professional, The Palace Papers: Inside The House Of Windsor - The Truth And The Turmoil has suggested.

Author Tina Brown claims that Prince Harry grew "angry" with his brother Prince William and also claims that "friction between the brothers escalated" after William became patron of the rhino and elephant charity the Tusk Trust in 2005, the Mirror reports.

The two feuding princes reportedly had "Olympic rows" and the author quotes a friend of the brothers who referred to Harry as "very, very angry man".

Harry and Cressida's two year relationship came to an end in 2014 with the duke writing a "sweet letter" to his ex which said: "I admire you, I wish you well and above all thank you for helping me to address my demons and seek help'' according to Brown.

The royal author also suggests that his former flame was the first person that persuaded Harry to seek help from a therapist.

She adds that it's proof that tension existed between Harry and William years before he had even met Meghan Markle.

However, she continues to say that the arrival of the former Suits actress changed "everything" in Harry's life, and claimed the couple became "drunk on a shared fantasy of being the instruments of global transformation who, once married, would operate in the celebrity stratosphere once inhabited by Princess Diana".

Mrs Brown previously claimed that Harry's relationship with the Prince of Wales was "never the same" after he tied the knot with Kate Middleton in 2011.

Theformer editor-in-chief of Tatler claims the brothers began to drift apart after Kate married into the family as William became more focusedon his marriage and life with his new wife.

Despite this claim, Harry once described the Princess of Wales as "the sister I've never had and always wanted" back when he shared a close bond with both his sister-in-law and his brother.

Join the Daily Record's WhatsApp community here and get the latest news sent straight to your messages.

Ms Brown also said, in her book The Palace Papers, that Harry and William's relationship changed further following the birth of Princess Charlotte in 2015.

She wrote: "Though they were still 'incredibly close, living next door to each other [at Kensington Palace], sharing the same office, and hanging out a lot.

"[Harry] mourned his us-against-the-world bond with William. He felt displaced by their bougie family unit, and couldn’t understand his brother's obsession with his in-laws. Bucklebury [The Middleton's home] world bored Harry to tears."

She continued: "[William and Kate] had a tight unit, and William [became] a full-on Windsor country bumpkin."

Harry and Meghan tied the knot in 2018 and less than two years later they announced their shock departure from the Royal Family in January 2020.

They moved to the US shortly after exiting the Firm and currently live in Montecito, California with their two kids Prince Archie and Princess Lilibet.

Get the latest celebrity gossip and telly news sent straight to your inbox. Sign up to our daily Showbiz newsletter here.