Chadwick Boseman took a salary cut so Sienna Miller’s pay could be increased on the film 21 Bridges, she has revealed.

Describing the late actor’s gesture as “about the most astounding thing that I’ve experienced”, she said it was “unfathomable to imagine another man in [Hollywood] behaving that graciously or respectfully”.

Boseman died in August following a four-year struggle with colon cancer, a year after the release of the action thriller that he also produced.

And Miller said that while she was unsure whether she should discuss the story, she had decided to do so “because I think it’s a testament to who he was”.

She told Empire magazine: “This was a pretty big-budget film, and I know that everybody understands about the pay disparity in Hollywood, but I asked for a number that the studio wouldn’t get to.

“And because I was hesitant to go back to work and my daughter was starting school and it was an inconvenient time, I said, ‘I’ll do it if I’m compensated in the right way.’

“And Chadwick ended up donating some of his salary to get me to the number that I had asked for. He said that that was what I deserved to be paid.

“That kind of thing just doesn’t happen. He said, ‘You’re getting paid what you deserve, and what you’re worth.’ It’s just unfathomable to imagine another man in that town behaving that graciously or respectfully.”

Miller said she had subsequently told male actor friends of Bosesman’s actions “and they all go very, very quiet and go home and probably have to sit and think about things for a while”.

“But there was no showiness, it was, ‘Of course I’ll get you to that number, because that’s what you should be paid’,” she said.

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In an interview with Sky News last November ahead of the movie’s release, she had spoken about how key he had been in changing her role from a male to female character – describing him as “the kindest, sweetest human being”.

“He was also a producer on this film. My character was originally written to be a man, and he was very influential in changing that. I think he’s a real champion for women, and I have deep, deep respect for him.

“I think that the world is changing in a way where those kinds of decisions are being considered in a way that they might not have been before. I’m obviously thrilled that they did make that decision because then I got to be in it.”