Sienna Miller almost 'died' when Kevin Costner offered her Horizon role

Sienna Miller metaphorically "died" when her teen crush Kevin Costner offered her a leading role in his Horizon: An American Saga film series.

The Layer Cake actress tried hard to keep her inner fan in check during a Zoom meeting with The Bodyguard star but she struggled to contain herself when he offered the role of Frances Kittredge.

"Kevin sent me the four scripts, and they were astounding, almost Tolstoyan in length and detail. They hooked me," she recalled to Harper's Bazaar. "Then he asked to Zoom, and I was thinking, 'Be still my Nineties heart!' because I had been obsessed with Kevin Costner growing up. He was my first love.

"So, we talked, and he was very complimentary. He told me the story of the film and got to know me a bit. At the end he said, 'Sienna, I have one question for you: will you go West with me?' I died. I said, 'I would go to Mars and back with you, Kevin.'"

The four-part series has been a longtime passion project for Costner, who invested his own money into the epic Westerns, which chronicle the pre-and post-Civil War expansion and settlement of the American west. He co-wrote, directed, produced and starred in the first two movies, while production on the third is underway.

Miller went on to explain why Frances resonated with her.

"If there's one thing I've gained from the life I've led it's a sense of resilience, fortitude - which sounds like I'm complimenting myself, but that's not how I mean it. It's like being forged in fire. I would have loved to have not been forced into that resilience, but I have, and that's a part of myself that I brought to Frances," she shared.

Horizon: An American Saga - Chapter 1 is in cinemas now, while Part 2 will be released in August.