Marilyn Monroe
John Huston who fought with MM so famously on The Misfits wanted the great MM to do this film but allegedly per Huston MM's pychiatrist urged she not do it.
Me thinks Huston was trying to settle a score and just said that. The point is that MM was the superstar of the world and why would she take a role supporting Monty Clift ( her good friend)...in those days, stars were stars.
Remember the quote from Spencer Tracy...when asked why he always got top billing over Katharine Hepburn..." This is a business not a Lifeboat")
I recall this was a Universal pic and MM was a Fox star with permission to do outside pics and she was negotiating with Universal to do Catherine the Great with Rock Hudson as Peter in Peter and Catherine.