The Dark Knight director Christopher Nolan has doubts over the next Batman movie – because the third film in the franchise may be too difficult to make.

Speaking to the Los Angeles Times, he was unsure if there could be another story that would keep him “emotionally invested” for the time it would take to make a sequel.

“On a more superficial level, I have to ask the question: how many good third movies in a franchise can people name?” he said.

“At the same time, in taking on the second one, we had the challenge of trying to make a great second movie, and there haven’t been too many of those either.”