Forest Whitaker spent months trying to shake off his portrayal of Idi Amin in The Last King Of Scotland, because he studied the African dictator so hard he started hallucinating - just like his subject did.

The Butler star reveals he went too far to play the feared Ugandan leader and the role really messed with his mind.

Whitaker tells The Hollywood Reporter, "I was playing a schizophrenic and every night I kept working really hard, pushing my head to the point where I started to see the things that I was imagining. I realised there is a way to screw with your brain.

"It took me a really long time to get myself back to thinking the way I wanted to - it almost took a year."

But the role was a big winner for the actor, who picked up a 2007 Oscar for his portrayal.