In a rare interview for new book, The Royals In Australia, Sir William reveealed 'nobody felt it right to go to bed before the Queen did.'
And while the tradition is something Meghan Markle may have to adopt now she’s an official royal, according to Sir William, it was something Princess Diana struggled with.
He revealed, 'For Diana the long royal evenings were agony.
'There’d be an hour or so in the sitting room of everyone sitting around making conversation, and nobody felt it right to go to bed before the Queen did.
'And Diana was driven to such extremes that she’d excuse herself and go to bed, which was thought to be rather bad form, going to bed before the Queen.'