The three actresses starred together in the 2018 drama, and although they were all leading ladies, only Olivia received an Oscar nomination for Best Actress - which she won for her role as Queen Anne - whilst both Emma and Rachel, who played Abigail Masham and Lady Sarah Churchill respectively, were put up for Best Supporting Actress.
And now, Olivia has revealed her co-stars - who both lost out in the Best Supporting Actress category - actively chose not to put themselves forward for a Best Actress nomination because they believed Olivia deserved the gong the most.
She told Total Film magazine, "What I didn't realise for the Oscars was that you are meant to say what category you want to go up for. I went: 'No, that's rude. I'm not doing that.' "
"And also because I felt that we were all three equal people - Emma, me and Rachel were three equals. I said: 'If they can't change it so that we can all be equals, then I don't want to do it, because it's not right.' "
"So I refused to say it. I said: 'We can either all go up for lead, or all go up for supporting.' "
Explaining the kind deed her co-stars had done in secret, she then explained, "But then what I didn't realise … someone let slip that Emma and Rachel had both decided - which makes me feel quite emotional - that they would go supporting to make me go lead, because they said they'd both had it, so it was my turn."
"Isn't that amazing? That's two incredible friends. I said I was not doing it unless we could all be equal. So they ignored me, and did something selfless and charitable."
And this year could see another big win for 47-year-old Olivia, who is up for two Golden Globes and two SAG Awards for her work in Netflix hit "The Crown" - in which she plays Queen Elizabeth II - and "The Father".
The Academy are set to announce the nominees for the 2021 Oscars ceremony on March 15.