Hannah Waddingham. Photo: Ben A. Pruchnie/Getty Images

Spoilers ahead for the most recent episode of Game of Thrones.

When Hannah Waddingham was cast in the role of Septa Unella — she of the stingy water rations — people started extending their congratulations by saying, “Oh my God, I’m so glad for Cersei to finally get her comeuppance, and you’re doing it!” Trapped in a cell, charged with fornication, incest, treason, and murder, Cersei’s short on friends at the moment. Her son, the king, is too forlorn to stop by, her brother/lover’s off in Dorne, and she’s alienated most of the Small Council, save for Qyburn. Her main visitor is a “faceless nun” who comes by to extract a confession, and dole out small amounts of food, water, and mistreatment. Waddingham chatted with Vulture about the chance to degrade Lena Headey, begging the makeup department for makeup, and what kind of undergarments Septas wear.

I don’t know if you knew this, but Amanda Peet was gunning for your role. And she kind of had an in, because she’s married to a Game of Thrones showrunner. She just really wanted to degrade Lena Headey …

Oh really? [Laughs.] Oh my God, that’s good to know, because I think she’s fabulous. I didn’t get to meet her, but David [Benioff] and I were comparing notes, because I had a 10-week-old baby in tow when I was in Croatia, and I think she was about to pop, with their third, so I guess that’s why she wasn’t there. Lena and I had a great laugh doing that, I have to say. We absolutely got on like a house on fire, and at times, we were told off by the director because we were just having way too much fun. It was actually more because I’m a smiley, wide-mouthed person in real life, and I think she just found it hilarious that I had to be really stern, and have this awful, scary face. So every time we tried to shoot, it was just like, “Hold on, we have to get ourselves together for a second.” [Laughs.] We were just two birds having a laugh together and had to pull into gear to get the job done.

Your character is torturing Cersei, in a way. Depriving her of sleep, depriving her of water …

She is, but in her eyes, she’s devout and she’s been chosen to take up the mantle here of being the main torturer. And she doesn’t see it as torture. She thinks she’s cleansing her, cleansing her soul. I think she’s trying to teach Cersei that you have to strip everything back. These are the most simple things — sleep, food, water, nobody talking to you, total isolation. At one point, I chuck a piece of bread at her, and I hit her with the ladle, and those are the only moments that we would call aggression. But it’s a dismissive gesture. That’s at least how I took it, because everything else has been passive, annoying, ignoring gestures. I asked, “Does that not make it look like Unella is getting irritated?” and they told me, “It’s not that she’s irritated, it’s just that she’s trying to limit, to silence her, because Cersei is trying to talk to her again.”

It’s a mind game. It’s breaking her down, making Cersei feel like she is nothing, not listening to anything she says, not letting it flicker on her face that anything has sunken in, and that drives Cersei even more to distraction. She gives nothing, even when Cersei is threatening her with her life. And to have someone screaming in your face, we would all naturally spit back. Septa Unella does not at all. She’s not fazed by Cersei at all. She’s absolutely unyielding. They don’t care who she is. I don’t think she knows her from Adam, other than what she’s been told: “We have a woman coming in, and she’s done these things, and we need to cleanse her.” So she’s extracting these deep layers from Cersei, without saying hardly anything to her at all. And Cersei feels small, for the first time, and by someone she’s never hurt, never even met before. Usually, everyone is moved in some way by Cersei. Usually, she gets results. But while she’s in that cell, she has to conform. Otherwise, there’s no way out.

If she wants Cersei to confess, why not talk to her? Engage her in conversation?

I wondered if Unella actually took a vow of silence. She must have, because she would say more, right? But she has to speak a few words, to get what she wants out of Cersei. I didn’t really want to speak as her, because she’s so devout, and she sees Cersei as a vulgar, deranged whore. [Laughs.] But for me, I think Cersei’s fabulous! Just beautiful. Glorious. And she’s absolutely looking after her family — not in the way we think you would, but we all have our own ways of doing things, don’t we? Part of the problem is that she has only yes-men advising her. It’s an absolutely lethal cocktail of somebody who is naturally autocratic having only yes-men around her. It just exacerbates the problem, doesn’t it? I think her meeting with the High Sparrow was just magnificent, when she realized, That’s not going to wash here.

Cersei’s not looking her best at the moment, but at least no one else in there does, either. What was it like shooting with no makeup on?

It adds another dimension to it, because you’re playing someone who has given up anything that makes the day softer, easier, more beautiful, and wants Cersei to see the error of her ways, and cleanse her. It took me to a place that I’ve never been before. As women, we’re not quite used to that. Cersei’s been stripped of her finery, of her vanity, which is her mask, and she’s got grubby, dirty feet. I’m sure Septa Unella doesn’t have any vanities, but come on! Can I have a little bit of concealer? Or bronzer, or something? A little bit of mascara? “No.” Right, then … [Laughs.]

The first time I went into the makeup trailer, we braided my hair really tight, so that you wouldn’t see any of it at all, put the wimple on, and then they brushed my eyebrows the wrong way, and then added in some hairs where most women would take them out! Like, seriously, is there a hidden camera somewhere, testing me? And that was it. Kicked me out the door, and then they said, “We actually wanted to break you down a bit,” and I was like, “No, no, no … This is fine, this is lovely, thank you!” They tried to come up to me on set, and I could feel them trying to do something on my lip, and I was like, “You’re giving me a cold sore, aren’t you?” [Laughs.] Seriously, I’ve already got to do scenes with one of the most beautiful women in the world — can you just stop? [Laughs.] I usually play quite glamorous parts in theater and on screen, so to have all of that stripped away, it’s giving you so much, before you’ve even had to think about it.

Before Septa Unella, the only other Septa we’ve gotten to know on the show was Septa Mordane. Sansa wondered if she had hair under the wimple. I’m wondering, what do Septas wear under their shifts?

Do you know what? In Croatia, as little as possible! Because it’s so damn hot. It was like having a really hideous, steamy hot spa treatment while you’re standing there filming. I actually said to the wardrobe department, “Can we seriously limit what’s going under there? I feel like I’m wearing a duvet.” [Laughs.] Oh my lord.