"That the royal family will be 'quaking in their boots' to see what explosive revelations Harry comes up with. To a certain extent there will be things in there that the Royal family would rather was not made public," he said. "But there will also be plenty of stuff in this memoir which works in favour of the monarchy back in Britain."
Prince Harry could still play a role during the Platinum Jubilee celebrations this year.
The historian does not believe the Duke of Sussex will use his upcoming book to "trash" his family and, even if he does revisit the allegations made against the family - including the incident with the "racist royal" referring to Archie's skin colour - it will be in a conciliatory way.
"During the Oprah interview, he was unwilling to name names, he was unwilling to point the finger of blame either at the Queen or members of his family," the historian said.
"The fact that he was careful in the interview, I think suggests the memoir will also be carefully presented.
"There will be gossip that helps sell the book but I don't anticipate there will be any great moment of reckoning that comes about because of this memoir," Owens added.
"I don't anticipate that he is going to really condemn any member of his family through public execution. It will be a cautious and careful presentation of his version of events."
Prince Harry's upcoming book, billed as "an intimate memoir" is yet to get a release date but it will come out just as the Queen celebrates 70 years on the throne.
The historian believes the book may actually end up being positive for "the firm".
