Prince William felt "utterly abandoned" by his younger brother Prince Harry and it will take a "long long time" for him to recover, according to royal expert Andrew Morton.
Morton, author of a controversial biography of Diana, Princess of Wales, said it is no surprise that Harry is returning to the UK, having sent several "smoke signals" about a potential reconciliation over the past year.
Surprise at speed of move
However, he added: "What is surprising is the speed with which they've moved… I find it amazing that they've chosen schools, somewhere to live. move the whole place out without sticking their toe in the water first."
Speaking on Times Radio, Morton said: "I think William has been deeply hurt by what Harry wrote and said about him, especially given the medical condition of Catherine and his father."
"This is a word I would like to use in relation to this relationship. William felt utterly abandoned and that word was used by someone very close to William. I think it's going to take a long long time for him to recover from that."
Sussexes' return to the UK
Harry and Meghan announced last week they would be returning to the UK later this month, having left the country six years ago when they stepped back as senior royals.
Their children, Prince Archie and Princess Lilibet, have been enrolled in British schools. It is understood the Sussexes will not be living in royal residences and their status will remain the same, rather than a "half-in-half-out" option.
The King, who is still living with cancer, was first made aware of the move on Sunday, only three days before it was made public, but is understood to welcome the opportunity to see more of the family both in a private and personal capacity.
Relationships with the Royal Family
He met with Harry and his family back in July, during the Duke of Sussexes' visit to the country to mark one year until his Invictus Games kicks off in Birmingham. Tensions have seemingly eased with his father.
Morton believes Harry will thrive by returning to his homeland. He said: "He's back with his friends, his family… members of his family that he still gets on with, obviously not William, and he can do his charity work."
"He's got the Invictus Games coming up in Birmingham next year. That's going to take a lot of organising. So, he's a happy camper."
William, meanwhile, is said to be still "smouldering with anger" at his brother over what was said during their six-year hiatus, according to BBC royal correspondent Jennie Bond.
The Wales' "want no part" in the Sussex drama, with sources saying William is "completely united" with the King in not allowing Harry and Meghan to achieve a 'half in, half out' role within the monarchy, after spending years railing against the institution. Friends of the couple have said while they "cannot forgive" the Sussexes for their hurtful accusations against the Firm, they are determined to "look forward to the future".
