Actress Lupita Nyong'o barely slept a wink while shooting 12 Years A Slave as the role was so harrowing it kept her awake at night.

The Kenyan/Mexican star scooped Best Supporting Actress at the 2014 Screen Actors Guild Awards and has been tipped as a hot favourite for the same honour at the upcoming Oscars ceremony for her gritty role as abused slave Patsey in the movie.

She has previously told how she tried to sleep with painful prosthetic 'injuries' on her back to experience the hell of her real-life character, and now she has revealed the part was so disturbing she would lie awake most of the night.

Nyong'o tells British magazine Hello!, "It was the height of summer (in Louisiana during filming) so you can imagine what it was like to be picking cotton in the middle of a field under a very hot sun. But we didn't complain because this was the reality of the slaves who have been there.

"I had insomnia for the entire time but that wasn't so much the heat as having to take myself to the painful place I had to go with my character. There was excitement, too, though - it was my first feature film, I was working with people I admired and we were making something that we all believed in."