Irish actor Michael Fassbender had to learn to ‘crack the whip’ for his starring role in the period drama ’12 Years a Slave’ - and come to terms with the demands of a controversial role.

The Kerry superstar plays slave owner Edwin Epps in the movie and has told reporters that he went to great lengths to prepare for the part.

They included constant practicing with a whip to perfect his skills so the punishment of his slaves was realistic on screen.

The 36-year-old said he found it uncomfortable to play a man so readily willing to inflict pain on other humans in order to control them.

The Western People reports that Fassbender believes his dedication to mastering the whip will be apparent to movie viewers.

He said: “I remember I had to practise on the whip; I had to learn to crack it properly. I remember thinking about the knot it created in my shoulder, the knot it would create from doing such a physical task as whipping the skin off another human’s back.

“That physical memory would stay in the body, my body, Epps’ body. The body would retain the memory of what you have done to your fellow man or fellow woman.

“What would the psychological effect of this be? The retention of pain in your body memory? It’s got to be stored somewhere. That’s what I tried to with Epps. There’s a deep conflict in the man.”

The is based on the 1853 autobiography by Solomon Northup, a Negro who was born free in New York State but was kidnapped in Washington, D.C. in 1841 and sold into slavery.

The movie also stars Chiwetel Ejiofor, Benedict Cumberbatch, Paul Giamatti, Brad Pitt and Sarah Paulson.