Tenet star Elizabeth Debicki says Kenneth Branagh struggled with the "darkness" he unleashed on her

Debicki told The Hollywood Reporter the gentlemanly Branagh struggled with the vicious way he had to treat her.

"The way I could probably sense the effect it was having on Ken was how gentle he was around the scene," she said. "On either side of action and cut, he was incredibly gentle. There was a real softness there and a real sensitivity, and I would say that he would often check in on me. In a funny way, when you play an estranged married couple for so long, you get to read each other very intimately and you become very aware of when the other person is perhaps struggling with something or if their mood drops or if they’re tired."

Debicki said the pair's relationship was "interesting... It’s sort of like a marriage, in a way."

She continued: "There were moments where I could tell that he was aware of what he was putting on-screen and the intensity and darkness in that character. And he knows me, and he knows that I’m a sensitive human being, obviously. And within that role, I received a lot of that energy; it was literally poured straight into my mind, body and soul. So I think that’s where I would see it manifest in him because he is really one of the nicest people on the planet."

Kat lives at the mercy of Andrei (Branagh), and Tenet's Protagonist (John David Washington), who uses her as a device to try and entrap Andrei.

Without giving anything away, Kat's story arc resolves in a satisfying fashion at Tenet's conclusion, to Debicki's approval.

"Let’s just say I was really looking forward to those [climactic] sequences," she laughed. "I knew that I was eventually going to play through those psychological shifts in her and that’s what I loved so much about the role.

"Some people have said things to me about how she’s captive or that there’s a kind of victim situation. And I don’t deny it because what I loved, in a way, was that it was really drawn into her in the beginning and we do find somebody who’s become victim to the circumstances of her relationship with her husband. But what I also found intriguing... was someone who had sort of become victim or almost prison to her own thinking about herself, what she was capable of and what she could or couldn’t do. And then, she does go on this enormous, psychological, often very high-octane, traumatising, at times, experience that does change her significantly."

Kat realises that she does have power over herself and over her own ability to survive something.

"She has this resilience to her, and I love that that was presented to me through this role and to the audience, I hope. In this genre, what we see her go through and what we see her do is not always a given."

Tenet is on general release at cinemas in the UK.

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