As well as starring as main character Elizabeth Mott, Larson served as an executive producer on the drama, having a hand in creating the world her character lives in. One addition was incredibly important to her - the inclusion of Aja Naomi King's character Harriet and her fight for Civil Rights.
Speaking about why that change was so important, Larson exclusively told RadioTimes.com: "That was a deviation from the novel but it was one that felt very clear to all of us.
"Books and TV and movies are just very different mediums in terms of what you are showing and what you are not showing, so with a book you can be very much in someone's head, and in their point of view, you're not imagining all of the people in the world. But with this show, it's really important to understand the context of the space that we're living in.
"It's Elizabeth going through this life, but what is going on at that time? So we just got so lucky to have such incredible consultants helping with that, and Aja is just such a beautiful person and a beautiful actress. It's one of my favourite parts of the show, to be honest. She just handles it so well. And it's very, very moving to me."
Meanwhile, Larson also felt the importance of doing the character of Elizabeth justice, especially after reading Bonnie Garmus's bestselling novel.
"I felt like Elizabeth was one of the greatest characters, it's just an honour and a gift, and so I take that very seriously," Larson explained.
"It's a big responsibility, and so I put everything into it that I could. I mean, spending two years developing something, you become very intimate with it, it became just a very long prep, maybe the longest prep I've ever done for something.
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"And it's like with anything like this, you go through the first maybe week or two, it just feels like, 'Oh, I must not be doing this good enough.'
"You know, there's this sense of trying to find it and then you hit a point where it starts to feel like it makes sense and it's inhabited, and then it's over. It's like, right when you start to get it is when the job is done. But that's what I love about it.
"I just have to trust that what I am bringing on a given day, and in a given moment, all I can do is be honest and that's it, and I don't think it's ever been my way to think about what it could be perceived as or if someone will like it or not – I don't think that's my job. My job is to just be there and to honour it and to fight for her."
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