Chris and Jonathan Nolan talk The Dark Knight!

Now that Christopher Nolan's latest pic - duelling magicians drama The Prestige - is ready to enter cinemas, he and his scriptwriting brother can devote themselves full time to working on The Dark Knight, the sequel to Batman Begins, which Chris co-wrote and directed and which Jonathan was a consultant for.

Out and about on the press tour for The Prestige, the pair has been talking about the new film - well, as much as they can, anyway. With the script still in progress, they're naturally being cagey as to what they'll reveal. collared them and asked about the development of the movie so far, including the script work so far: "We keep it very close to the chest. We've been working on the script for a long time, over a year now one way or another with David Goyer and my brother, but it has to be right. We are almost finished. You want to know what page I'm on?" laughs Nolan. "I wouldn't tell the studio that, I'm not going to tell you that! What I will say is it's coming along. We've finished constructing the Joker's character and so we we've been able to think about that." He admits that casting Heath Ledger as the grinning villain was down to more luck than anything else. "You know, his casting was a series of fortunate events, he expressed an interest. I hadn't really thought that he would be interested in doing it but it was worth a try so it was actually a very early conversation. Then, you know, we realised we were seeing the same character."

As for Jonathan, he's even less forthcoming about the screenplay: "There's actually a Warner Brothers team of ninjas that will double execute me if I say anything about the script!" But he wasn't above dropping a few choice hints when asked about Batman being a detective in the new film. "Wouldn't that be great? That would be fantastic. I would love that, that would be wonderful," he smiled.

And what about Harvey Dent, AKA Two-Face? Chris confirms that Dent should be in the movie, but won't confirm if he'll be turning into his evil alter-ego. Oh, and apparently there's no-one in the Dent role yet. "I don't know who is going to be him and I am the only person who would know so... I don't know. We'll have to know fairly soon - we're shooting in February…"

Finally, there was the most important question: which of the brothers is the bigger comic book geek? "You know it's funny, I've told this story a couple of times. At the risk of sounding like I'm repeating myself, when I was 14 years old, my brother... I was not a big comic book fan when I was a kid, a little bit of this a little bit of that... but Chris gave me a copy of Dark Knight Returns for my birthday when I was 14 and that was it," says Jonathan. "That was the only superhero that I was interested in. Fifteen years later to the day, last year we went to the premiere of Batman Begins. It was really, really cool to be there because Batman is really the only, well, as you know he's the best superhero. For me he was the only superhero, so to work on that sort of material doesn't happen often but when it does happen you just feel very, very lucky."

For more of the interview, head on over here.