Cooper Struggled Playing 'Horrible' Hussein

The Mamma Mia! star took on the challenging role of the Iraqi dictator's son Uday in the film, as well as playing Latif Yahia - the man forced to act as Hussein's body double.

Yahia, who wrote the book the film is based on, was recruited to pretend to be Hussein from the age of 12, and was even made to undergo painful cosmetic procedures to enhance the likeness between the pair.

Cooper insists the roles have been his toughest to date - because he struggled to grasp how the two men could have grown up to be so different.

He tells the BBC, "It's quite a horrible part. It was a difficult challenge, trying to understand who this guy (Hussein) was and why he did such unbelievably terrible things, and then to play this innocent guy (Yahia), who he forced at gunpoint to be his body double."