Article continues below advertisementOK! can reveal Kate Middleton is said to have reached a painful conclusion ahead of the 30th anniversary of Princess Diana's death - that she must stand firmly beside Prince William rather than attempt to broker peace with Prince Harry.August 2027 will mark three decades since Diana was killed in a Paris car crash in 1997 at the age of 36. The milestone falls just weeks after the Invictus Games, founded by Harry, 41, which will take place in Birmingham next July. With Harry and Meghan Markle, Duchess of Sussex, 44, expected to be in the U.K.