'I lost my mind - I genuinely thought we were these people' - Margot Robbie on being 'almost delusional' for I, Tonya

Margot Robbie stars as former US figure skater Tonya Harding in I, Tonya

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Margot Robbie says she "lost [her] mind" shooting I, Tonya.

The 27-year-old actress immersed herself so deeply in playing disgraced skater Tonya Harding, she forgot where the character ended and in scenes opposite Sebastian Stan as her abusive husband Jeff Gillooly, she "genuinely thought" their arguments were real.

In an interview with Grazia magazine, she admitted: "I had lost my mind. I genuinely thought we were these people and we were off the set, running down the street screaming at each other and the cameras are running after us. I think I was screaming something about needing to go to hospital because my hand was broken.

"It wasn't, but I was so caught up in the moment. And Sebastian was like, 'Margot, where are you going?' He went to pick me up because I was continuing to tear down off set and I turned and punched him in the head."

Margot Robbie in I, Tonya

The incident only stopped when the crew cut filming, and though they were "scared" by her behaviour, she found it "exhilarating".

She said: "A few times I've genuinely thought I wasn't on set and that I was that character in that time and in that place. To truly forget there's a camera in your face is really hard. When it does happen, it's really exhilarating. I don't know if it's because you're so tired when you're filming you're almost delusional."

Margot Robbie in I, Tonya

During filming, Margot lost all feeling in her arm and had to undergo weekly MRI scans which showed she had injured her neck.

She said: "I don't think [the numb arm] was connected to the skating.

Margot Robbie (L) and Sebastian Stan attend the 'I, Tonya' New York Premiere at Village East Cinema on November 28, 2017 in New York City. (Photo by Dia Dipasupil/Getty Images)

"[I had the scans] to make sure we weren't doing any real damage. I herniated a disc in my neck."

'I, Tonya' documents one of the most infamous scandals in sporting history as it follows the true story of Tonya and her husband when they plotted to attack her rival Nancy Kerrigan before the US Figure Skating Championships in 1994.

The conniving couple secretly hired a thug to break Nancy's leg so that she had no choice but to pull out of the then-upcoming Winter Olympics but, despite her injuries, the pair went on to compete against one another in highly publicised sporting event.

Nancy remarkably won the silver medal in the Games and, after details of the crime - known as The Whack Heard Round the World due to the fact she was clubbed around the knee with a baton - came to light, Tonya was dished out a sporting lifetime ban.

Her husband Jeff, on the other hand, was handed a two-year prison sentence.