'That goes back to JRR Tolkien writing The Hobbit first, for children, and only after did he develop his mythology much more over the 16 or 17 years later when The Lord of the Rings came out, which is way more epic and mythic and serious.

What people have to realize is we've adapted The Hobbit, plus taken this additional 125 pages of notes, that's what you'd call them. Because Tolkien himself was planning the rewrite The Hobbit after The Lord of the Rings, to make it speak to the story of The Lord of the Rings much more. In the novel, Gandalf disappears for various patches of time. In 1936, when Tolkien was writing that book, he didn't have a clue what Gandalf was doing. But later on, when he did The Lord of the Rings and he'd hit on this whole epic story, he was going to go back and revise The Hobbit and he wrote all these notes about how Gandalf disappears and was really investigating the possible return of Sauron, the villain from The Lord of the Rings. Sauron doesn't appear at all in The Hobbit. Tolkien was retrospectively fitting The Hobbit to embrace that mythology.

He never wrote that book, but there are 125 pages of notes published at the back of Return of the King in one of the later editions. It was called The Appendices, and they are essentially his expanded Hobbit notes. So we had the rights to those as well and were allowed to use them.' Said Jackson: 'We haven't just adapted The Hobbit; we've adapted that book plus great chunks of his appendices and woven it all together. The movie explains where Gandalf goes; the book never does. We've explained it using Tolkien's own notes. That helped inform the tone of the movie, because it allowed us to pull in material he wrote in The Lord of the Rings era and incorporate it with The Hobbit.'