The Irish actor played the ancient Greek conqueror in the 2004 Oliver Stone project, co-starring Angelina Jolie and Val Kilmer.
It was panned by movie critics and only managed to recuperate one quarter of its $155 million (£97 million) budget back at the U.S. box office.
But Farrell was shocked by the movie’s reception – as he and his co-stars were sure it would sweep the board at the 2005 Academy Awards.
He tells Britain’s Total Film magazine, “We were splitting the atom on Alexander – we were really doing something that had never been done and we were telling an epic tale that would harp back to the days of Cecil B. DeMille and we were going to get 12 Oscar nominations. In our heads. That’s one case of where we completely misjudged the situation.
“It was a very big story and I know that Oliver was very rushed to do a cut, but for me it just failed gloriously. It just kept in step with the magnitude of Alexander’s ambition and ego.”
And Farrell is still upset his dyed blond hair wasn’t properly maintained for the duration of the shoot: “That was unfortunate. We f**ked that up. A $150 million film and we couldn’t sort out my roots.”