Peter Morgan (showrunner) starts a new relationship with Jemima Goldsmith,a close friend of Lady Diana
This means he could write scenes for season 5 about events or conversations not know to the pubblic. Very good. Or maybe he will side with Diana in season 5. We'll see.
https://www.dailymail.co.uk/femail/article-9159333/Could-Peter-Morgans-new-relationship-Jemima-Goldsmith-change-season-Crown.html