The next James Bond movie Skyfall promises a journey into the troubled psyche of the iconic spy and revisits the original books by Ian Fleming, according to director Sam Mendes.

"You always go back to the Fleming because the character Fleming created over a number of novels was incredibly complex," Mendes said at a news conference in Istanbul, where the crew of Skyfall has filmed.

"Some people sometimes forget in the cliche of Bond, which is the international playboy, and someone who's always untroubled, and almost never breaks a sweat, that actually what (Fleming) created was a very conflicted character," said Mendes, who was joined by cast members including Bond actor Daniel Craig.

In Fleming's last novels, Mendes said, Bond suffered from a "combination of lassitude, boredom, depression, difficulty with what he's chosen to do for a living, which is to kill. That makes him a much more interesting character, and some of those things are explored in this movie, because Daniel as an actor is capable of exploring them."

It is Craig's third portrayal of the spy, and he introduced a darker side to Bond in his earlier roles in 2008's Quantum of Solace and Casino Royale in 2006.

Craig reread Bond novels as part of his preparation for Skyfall and a delay in film production, caused when studio MGM filed for bankruptcy in 2010, allowed him more time to discuss the character with Mendes. He said he had spoken to intelligence agents about their work, and has some inkling of the hardships they face.

"I've got the better job," said Craig.

Skyfall is due for release on October 26. Judi Dench returns as spy chief M and the film introduces Naomie Harris as a field agent named Eve and Berenice Marlohe as a character named Severine.