Christopher Nolan ''never'' planned to make a second or third Batman movie but after helming 'Batman Begins' he was eager to find out what would happen to Batman/Bruce Wayne in the future.
The 41-year-old filmmaker admits he didn't ever intend to make a sequel to his 2005 film 'Batman Begins', but as soon as the storyline had been established then he knew a second movie in the franchise had to come to life to see what would happen on Batman/Bruce Wayne's Journey.
Writing in the forewood of new book 'The Art and Making of The Dark Knight Trilogy', he explained: ''I never thought we'd do a second - how many good sequels are there? Why roll those dice?
''But once I knew where it would take Bruce, and when I started to see glimpses of the antagonist, it became essential.
''We re-assembled the team and went back to Gotham. It had changed in three years. Bigger. More real. More modern. And a new force of chaos was coming to the fore. The ultimate scary clown, as brought to terrifying life by Heath. We'd held nothing back.
''I never thought we'd do a third - are there any great second sequels? But I kept wondering about the end of Bruce's journey, and once David and I discovered it, I had to see it for myself.''
Christian admits working on the Batman trilogy was the ''most challenging and rewarding'' experience in his career and he will ''miss'' the superhero.
He added: ''My time in Gotham, looking after one of the greatest and most enduring figures in pop culture, has been the most challenging and rewarding experience a filmmaker could Hope for. I will miss the Batman. I like to think that he'll miss me, but he's never been particularly sentimental.''