Prince Harry was left on read in the hours before his grandmother, Queen Elizabeth II, died last year -- and the person ghosting him was none than his brother ... William.
A new book from Royal insider Omid Scobie makes the shocking claim ... namely, that Bill completely ignored Harry's texts as he was attempting to make travel plans to fly from California to the UK in hopes of seeing QE2 before she passed.
One source says all of Harry's messages to his old sibling went unanswered -- with the apparent rationale being ... "He clearly didn't want to see his brother."
Since William wasn't communicating with Harry ... Scobie's book -- "Endgame: Inside the Royal Family and the Monarchy's Fight for Survival" -- says the Duke of Sussex had to figure out what was going on all on his own ... which required him to book a pricey private jet.
Scobie alleges Harry had to shell out $30k to fly over solo ... this as PW was on his own private flight with Prince Edward and his own wife. The book claims Harry had no idea if the Queen had died already or not ... and word of her death actually broke while he was in the air.
As far as how Harry supposedly felt about this .... Scobie cites a source as saying, "Harry was crushed. His relationship with the Queen was everything to him. She would have wanted him to know before it went out to the world."
This anonymous pal of Harry's adds, "They could have waited just a little longer, it would have been nothing in the grand scheme of things, but no one respected that at all."
Of course, when Harry did finally arrive in Scotland -- where the Queen was on her deathbed before eventually passing on -- it was too late ... and he hadn't had a chance to say goodbye.
His presence in the UK at the time was solemn -- and while he and Will put on a united front to commemorate their grandma ... this book now suggests things were incredibly frost between them behind the scenes. Now, with their recent history in mind ... that's no shock.
Fact is ... Harry and Meghan's infamous claims of racism within the Royal institution included a hint that perhaps William himself had partaken in all that -- something the Prince of Wales firmly denied at the time. It's an understatement to say ... Will didn't like how Harry handled his exit as a Senior Royal, and everything else that came afterward -- public and otherwise.
Even now, their relationship seems icy at best ... there are reports that claim William won't "shed a tear" if Harry and Meg don't make it for Christmas time festivities in the UK.