[Editor’s note: The following contains spoilers for Red, White & Royal Blue.]From director/co-writer Matthew López and based on the best-selling book by Casey McQuiston, the romantic comedy Red, White & Royal Blue follows Alex Claremont-Diaz (Taylor Zakhar Perez), the son of the President of the United States, and Prince Henry (Nicholas Galitzine), Britain’s spare heir, as their relationship evolves from total disdain into friendship, and then something even deeper. When friction turns into undeniable chemistry, the two young men must decide how far they’re each willing to go for love, as they challenge tradition, duty and expectations.

During this 1-on-1 interview with Collider, López talked about the connection he felt to the material when he first read the book, what made Perez and Galitzine the perfect actors to take on these characters, the importance of finding the right chemistry, the scenes he felt the most responsibility to get right, how many times they needed to shoot the destruction of the cake, and approaching the intimacy in collaboration with the actors and an intimacy coach.

Collider: You first came onto this project to work on the script, but ultimately ended up directing it. Was that something that was like always in the back of your mind?

MATTHEW LÓPEZ: I read this book at a period in my career where I knew that I really wanted to get serious about making a film. The Inheritance had just opened on Broadway, the time was right, I read this book, and it just happened. I read it in February of 2020 and not only did I know that I was ready to make a film, but I wanted to make this film. So, the idea for me was always to direct this movie. What I had to do is just sell myself and my vision for this film to Berlanti/Schechter and to Amazon.

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Was there a moment when you realized everybody was on board and it was actually going to happen?

LÓPEZ: It was a rolling sense. There was the moment I was approved as director. Then there was the moment that we hired casting directors. It really started to really get serious when, when Nick [Galitzine] and Taylor [Zakhar Perez] met for the first time on Zoom. Up until that point, I knew there was a chance that it would fall apart. One of the things I said, and I don’t think it was controversial, was that, if we can’t find the right actors, there’s no movie. I didn’t want to make this movie with the almost right actors. So, when I got the two of them on Zoom together and they had instant chemistry and they liked each other straight away, I knew that I was gonna be busy for the next two years of my life.

Did you have any idea whether their chemistry would work? When you were talking to each of them individually before they had that moment together, were you worried at all?

LÓPEZ: There was a lot riding on that chemistry. You can imagine what that moment is like. I liked them both so much, individually, and I knew that, individually, they were perfect for the roles. They were absolutely perfect. I found Nick to be an actor who I could really place the character of Henry into the care of. He was a real loving, gentle caretaker for that role. And in Taylor, I found someone who was just absolutely dynamic and alive and exciting as Alex. But I knew it would do me no good, if the two of them just didn’t work together and I didn’t believe it. And, my God, I believed it from the second it started. Everybody on that Zoom knew it, too.

You get a bit of wish fulfillment in a story like this. There is a little bit of the fantastical because, even if we can relate to these characters on a human level, most people can’t necessarily relate to being the son of the president or being a prince in the monarchy, so it really feels like casting is something that really matters. It’s the thing that makes the audience connect with all of that.

LÓPEZ: Absolutely. One of the secrets of the book, and the thing that I knew I needed to tap into in this movie, is that the fact that they are basically both princes is honestly not why people love the book. They love the book because these two characters are such well-drawn, sympathetic, dynamic people. The secret to the book’s success is that Alex and Henry transcend their situation. You get to enjoy all the trappings of royalty and the monarchy and the White House and government, and all that stuff. It’s the best of The Crown, and best of The West Wing. However, it really is about going into their hearts and minds. Everything else just becomes scenic design and costume design. What really matters is these two individuals, and I think people really connect very personally to them. And I knew that, once I had Nick and Taylor, half my work was done for me.

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What were the scenes from the book that you knew you had to get right? Was there one that you felt the most pressure or responsibility for?

LÓPEZ: Honestly, the opening scene was so tricky for me because, not only is it the opening, but you have to always get your opening right. If you screw up the opening of whatever the movie is, then you’re dead. But I also knew that this was a very iconic opening to a novel. And on top of that, it was a very technically difficult scene to film. It was hundreds of extras, it was cake, it was a vision, it was choreography through space, and it was a lot of dialogue. That was three days of me, just gritting my teeth. I can’t tell you that I had fun on those three days. I knew that I had to get it right, in so many different ways. But I had a great team, and I had Nick and Taylor, and we got through those days. When people see the movie, you don’t see all the real effort that went into that filming that scene.

What was it like to shoot that whole cake moment? How many times did you have to shoot that? How many cakes did you have?

LÓPEZ: It’s funny, most of the shots of the cake, we used a Styrofoam and latex cake. We did that section of the scene for two days and you don’t want it to melt or go rancid. It was actually so lightweight that our production designer laid on the floor and had her team drop it on her head, just to show everybody that it was safe. Eventually, we had to put the boys on the floor and throw it in their faces. Me and my production designer were the ones, off camera, throwing it in their faces. We got it perfectly on the first take, and we looked at it and just decided, even though we had multiple costumes and a plan to give them showers and do their hair and makeup, I would have lost at least 90 minutes, every time I did that. So, I said, “We’ve got it. Let’s move on.” We actually got that in one take.

There are a couple moments where these guys kiss and there are some moments of them fooling around, before you have the longer sex scene. Did you have a very clear vision of what you wanted from that moment? Did it evolve out of collaboration with the actors? How did you figure all that out?

LÓPEZ: It was a real lengthy conversation between myself, my intimacy coordinator, Robbie Taylor Hunt, Nick, Taylor, and Stephen Goldblatt, my DP. What was most important to me about that scene is that we showed two characters having a life-changing experience. We needed that. I wanted it to look beautiful. I wanted it to feel tender. I wanted it to be sexy. I also wanted it to operate on a physical logic that leaves no doubt in the audience’s mind, what precisely is happening, at any one moment in the scene. But the most important thing to me is that we captured in their faces, the wonder and the newness, and perhaps the fear, the trepidation, and the excitement. By the end, we ended up framing much of that scene on their faces and their shoulders because I just wanted to let those actors play the scene on their faces. But it took weeks and weeks and weeks of conversation and rehearsals. That was the second most technical scene that we had to film.

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Did you always also want to include the mother-son safe sex talk after that? That’s just such a funny moment.

LÓPEZ: Just getting to be on set with Uma [Thurman] and Taylor, that day. Just playing the scene, I remember Uma stopping for a moment and just shaking her head. I was like, “What’s up?” And she just went, “She’s just so cool.” I was like, “Yeah.” And she was like, “Man, I wish she was real.” In that scene, I just really wanted to give the audience a sense of a mother who gets it. It helps that she’s President of the United States because you also want a president who gets it like that.

She’s also very prepared, when it comes to her response.

LÓPEZ: I love Taylor’s performance in that scene because Alex, in that moment, is just like, “Oh, my God, mom, you need to stop it!” For as cool as Ellen is and as prepared for this conversation as she is, the comedy comes from the fact that Alex is, in no way, prepared for his mother to be that prepared.

How much fun is it to turn Uma Thurman into the president? What was the whole experience of working with her like?

LÓPEZ: It was such a wonderful thing. From the day I first encountered her, as a moviegoer, I’ve just loved her. It was a real blessing to have her there with us. She came to this film with the exact same set of desires for the character that I had. We had a lot of conversations about how, in American politics, women in power often have to sacrifice their understanding of their own femininity, in order to attain and hold onto power. What was most important to her and I was that Ellen can both be powerful and maintain her definition of femininity for herself. I included Uma in conversations about costume design, production design, and of the oval office set. When she walked onto the set, I have never encountered a more prepared actor. She understood, implicitly. She already understood why every piece of furniture was chosen for her. She understood why every article of clothing was there. It was a master class in prepared acting. She really rose, and she brought everybody’s game up.

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There are such great moments from all of your supporting cast, too.

LÓPEZ: I really hope that everybody this summer knows the name Rachel Hilson and sings that name with delight. She’s so great in this movie. She is, especially, someone who is hopefully gonna be more widely known because of this film.

In adapting a book, we always hear about the desire to recreate the feeling the book gave when you read it. Did you get that feeling, watching the actors on set, delivering those moments, or did it take getting into the editing of this and seeing what you actually had, to really get that feeling?

LÓPEZ: It was both, depending on the scene. I remember there being moments on set when Nick or Taylor did something that was either so hilarious or so heartbreaking. We all tried our best to maintain composure, off camera, at our monitors, and yet those two actors were giving such committed, fearless, emotionally connected performances that, throughout many moments on set, they brought me, Stephen Goldblatt, and the crew to tears. By the end of the shoot, we were all rooting for them, as actors. They were delivering at such a high level of achievement, every single day, that cutting this movie was an embarrassment of riches. It really was.

Red, White & Royal Blue is available to stream on Prime Video.