Manville succeeds Vanessa Kirby and Helena Bonham Carter in the role.
However, when she heard showrunner Peter Morgan wanted to meet with her, she immediately assumed she was in line to play the Queen before Imelda Staunton was cast.
Manville told The Times she was asked: “Can you go to Peter Morgan’s house on Monday?” adding: “That’s how it happened for me, and I think it happened for Imelda. I never thought of myself as a Margaret. My immediate thought was the Queen, the Queen!”
She continued: “My agent said, ‘He wants to talk to you about playing Margaret.’ I thought, ‘Hang on a minute – Margaret? I can’t do Margaret.’”
Manville’s reasoning for thinking this was due to the fact she does not see herself as “glamorous”.
“In my head, I saw Margaret as young and glamorous, when Vanessa played her, and glamorous and still quite young, but a bit older, when Helena played her.”
The actor said she is unable to see herself in the same way as her predecessors, calling it a “problem with her own self-image”.
Manville said that, despite this, she was “really chuffed” to be offered the role.
The actor joins new cast members Staunton, Jonathan Pryce (Prince Phillip), Dominic West (Prince Charles), Elizabeth Debicki (Princess Diana) and Jonny Lee Miller (John Major).
The Crown season five will be available to stream on Netflix from Wednesday (9 November). Find The Independent’s first-look review here.