Royal biographer Angela Levin says Harry's behaviour has "changed enormously" since he married Meghan Markle, with the Prince now being "hard as nails", spiteful, and revengeful.

"When I was writing his biography he was charming, charismatic," Ms Levin told Sky News Australia.

"I don't recognise him now."

"He's as hard as nails, he's spiteful, he's revengeful."

Ms Levin spoke to Sky News Australia as part of a special report ahead of King Charles III’s upcoming coronation.