She plays Dido Lindsey, a mixed raced girl who was raised in high standing due to the position and influence of her father. However, due to her color, there are still social stigmas against her. As the film progresses, her eyes are gradually opened to more truths about her race and identity as she breaks out from her sheltered living and begins to attain knowledge and information about the injustices around her.
Dido is a well rounded character that displays character growth as the film progresses. She's not blinded by her race, but due to her upbringing, she never really had to worry much about it until she grew up. The film allows her to come to understanding about the world outside, especially in the height of the Zong slave ship case. It would take a great actress to bring out the innocence and change in Dido's character.
Gugu Mbatha-Raw has perfectly embodied Dido, doing the character justice. From the moment she has stepped in frame with Elizabeth, she hasn't faltered from the character. Dido undergoes a lot of personal development, and Mbatha-Raw was able to hit the notes perfectly. She flawlessly shifts from innocence, to fear, determination, and acceptance. Her role is lauded with content, and with one wrong shift of tone or action can bring a different interpretation to the character. Mbatha-Raw has immersed herself in the role that it's hard to distinguish between her and the character. Taking into consideration her performance in Beyond the Lights, you know it's a completely different Gugu Mbatha-Raw; in this case she became Dido, and Dido became her.
When someone has a great performance, there's usually a defining point that would make people say 'wow'. I didn't find that here. Because of the constant changes her character goes through, she has an array of 'defining' moments that really don't look that way because she is constant with her performance. She knows the kind of emotions her character is supposed to emulate, and she performs. Even at the height of emotionally charged moments, she doesn't take a dramatic hysterical road because she knows that's not what her character would do. Despite displaying a plethora of emotions in heated moments, you still get the sense that she is attacking the issue in a level headed manner, that she is taking everything around her in consideration - that's what Gugu Mbatha-Raw makes you see.
There really isn't any argument to make you see how fantastic she was here except to see the film yourself. I'm hoping she gets more leading roles and diversify herself in different genres and settings. I have seen her play two entirely different characters and has immersed herself in those roles. Based on those two films alone, I think she can have a fruitful career if provided with more opportunities.