Screen star Morgan Freeman was chosen personally by Nelson Mandela to portray him in a movie - but they're finding it a struggle condensing the life of the iconic politician into a film.

The DREAMCATCHER actor has been working on the former South African President's biopic for a number of years now, and the two men have struck up a valuable friendship through the project - despite the exhaustive process of trying to fit Madela's life into a conventional movie.

Freeman explains, "We are going to use (Mandela's) own book. But that is 700 pages and squeezing it down to a two-and-a-half hour movie is a very difficult job. That is why it is taking so long. To get all the points that are necessary, and leave out the ones that are not possible, it is very hard to do.

"He is a big fan, it was his choice that I play the role."