Peter Jackson: The script always had the movie of The Two Towers finishing with the return to Isengard and confronting Saruman in his tower. It just ended up being obvious to us when we cut the film together that having put the audience through not just the battle of Helms Deep but the immediate aftermath when the Riders charge down a causeway, Gandalfs at the top of the slope, and he charges down. Its just this almost biblical climax. Then youre also intercutting that with the flooding of Isengard.
To then actually have a six- or seven-minute dialogue sequence where they confront Saruman at the end of the film, just felt very anticlimactic. There seemed to be a natural conclusion to the film, you know: Hey, weve sat here for three hours. Okay, weve seen the big battle, now its time to go home.
We though, Well, hang on. There is an alternative here. If we have the confrontation with Saruman as an opening scene in Return of the King, it actually is gonna work better, in terms of the movies to be an opening of a film, not the climax of a film.