Gillian Anderson is letting fans in on some of the behind-the-scenes work that went into her transformation for a recent role.

According to the actress, she went to extreme lengths to play Margaret Thatcher on the upcoming season of The Crown. The 52-year-old actress joins Netflix’s beloved royal drama for season four.

Anderson recently chatted with OK! Magazine about playing the former U.K. Prime Minister and revealed she had to wear a fat suit while on set as a part of her unbelievable transformation.

“I wear a fat suit,” she explained. “And she has a very particular way of walking.”

But for the actress, the suit actually helped pull Thatcher’s entire look together and made the whole thing real after practicing for the role for so long.

“After you’ve been working on a character for a long time, it’s really quite something to see everything come together at the same time.”

“It’s daunting, too,” she continued. “The first time you step in front of the camera, you’re exposed and it’s being documented – and you hope you’re on the right track. It’s exciting to finally get there and it’s also a bit freaky.”

In the end, Gillian is proud of the work she put into the role, and she came out on the other side with some useful perspective about just how important a character’s voice is.

“It wasn’t too hard to maintain because she has a lot of breath in her voice. It was fun to do, but it was also a bit challenging to figure out how to not go too overboard and take it into parody. Ultimately, her voice is as quintessential as her wig.”

In preparing for the show’s premiere, Gillian also spoke to Harper’s Bazaar about the role earlier this month, insisting she and her partner, Peter Morgan, had ’very clear boundaries’ when they worked together on The Crown. Peter is the show’s creator and writer.

“For our own sanity, and actually for the benefit of the relationship, we had very clear boundaries,” Gillian told the publication. “I am not going to comment on the script, but you are not allowed to comment on the performance!”

And when it came to playing such a controversial figure like Thatcher, Gillian reveals she did not let her personal opinions of the former prime minister‘s policies impact how she portrayed her.

“I had to get to a point where it’s nothing to do with my opinions of her policies, of her actions,” she admitted. “It is only about her as a human being and her motivation as a politician and as a mother.”

Season four of The Crown premieres on Netflix on November 15.