Whisky got Margot Robbie through NZ shoot

Chris Pine, Margot Robbie and Chiwetel Ejiofor star in Z for Zachariah.

One day of filming for Z for Zachariah was so unbearably cold, Margot Robbie and her co-stars had to keep warm by swigging whisky.

The Australian star plays a woman who believes she's the last person on earth after a nuclear event, until two men appear (Chris Pine and Chiwetel Ejiofor) and begin vying for her attention.

Adapted from the post-apocalyptic sci-fi novel by Robert C O'Brien, it recently screened at Sundance Film Festival, where the cast sat down to chat with The Hollywood Reporter.

When asked about the worst day on set, Robbie immediately brought up a scene filmed in a river.

"You know how you always hear actors go 'oh we had to be in bikini when it was cold'. We literally had to swim in the middle of a night in this river and it snowed the next day," she says.

"That's how cold it was. It snowed the next day."

As for how they kept warm, Robbie says whisky was a key factor.

"It sounds like a party. But literally whisky and a hot tub."

It was so traumatic, it seems Ejiofor blocked it from his memory.

"I even forgot about that. I actually blacked it out," he says.

Pine recalls that the cold was especially awkward because it was during a scene where he was meant to be flirting with Robbie's character.

"I had my hair sticking up, turning blue. It was awful," he says, laughing.

- AA[