Australian actress Margot Robbie is getting the best reviews of her career for the biopic I, Tonya, which tells the tortured story of US figure skater Tonya Harding, who notoriously was involved in an attack on her rival in the run-up to the 1994 Winter Olympics. Robbie also produced the film, which costars Allison Janney and Sebastian Stan. And she loved screenwriter Steven Rogers' blackly comical tone.

Margot Robbie in 'I, Tonya'Margot Robbie in 'I, Tonya'

"It's definitely dark," Robbie laughs. "Allison Janney puts it well. She's like, 'It's like laughing in church when you know that you shouldn't, and then you're thinking what kind of person am I to find this funny?' It does have those moments in it."

Robbie believes that the story itself helped create the film's tone. "You've got the mockumentary feeling, the very dark comedy, real life events, real life people," she says. "You've got an event people remember, but have very strong feelings about. These characters are amazing, so flawed and wrong, and yet you empathise with them in a weird way. You can see a bit of yourself in them at times. There was a real opportunity to surprise people."

Indeed, in order to get into the role, Robbie had to identify with Harding, who is still perceived as a villain. "In the beginning, I wasn't really sure," she admits. "There were things that didn't add up. Facts were muddled. But the more I became Tonya, the more I saw things from her point of view. I'm on her side 100 percent. I don't think she did anything but be different from what the world wanted. There are cool misfits, and then there is Tonya. She didn't fit in. And I love that."

An even bigger challenge for the 27-year-old Robbie was playing Harding from age 15 to 44 and learning to ice skate. "I did four months of training, five days a week, four hours a day," she says. "On Christmas Eve, I was at the rink. And now I actually really miss it. I kept my ice skates, but I said goodbye to a whole world of pain that I didn't realise came along with figure skating."

More: Nine other celebrities who played sports legends on the big screen

And she also enjoyed stepping up to play a lead role. "It's the first time where the title is also my character's name," she says. "I have never done that before. I was Jane in Tarzan. And I wasn't the Wolf of Wall Street, Leo was. This was the first time that I really had the weight of the film on my shoulders."