He has always been a science fiction fan and the futuristic yet volatile world of Mega-City One was intriguing and "wonderfully escapist" to him.
"I just enjoy these stories, they are great morality tales set in a totalitarian society that is teetering on the brink of chaos and the only thing that's holding the whole show together are the judges who, as a desperate measure, have been forced to get out from behind their desks and courtrooms and get on the streets and dispense justice."
So Urban was well qualified for the role and it was this knowledge and passion for the character that helped score him the part.
Another thing in his favour when he met with producers was his insistence that there should be no scenes with Dredd not wearing his helmet.
"A lot of the producers' concerns with who they were going to cast was whether the person was going to turn around halfway through the shoot and demand scenes without the helmet.
"I just reassured them that, 'If I had read the script and there was a Judge Dredd without a helmet on then I wouldn't have met with you'," he says with a laugh. "It was pretty clear we were all on the same page".
And Urban and Wagner, whom he met during filming, were also both in agreement that "Dredd says less" after they had read writer and producer Alex Garland's initial script.
"If you can say it in one word then don't take a whole sentence," says Urban with a laugh.
So the script was made even leaner and meaner with lines like, "You have been judged. Sentence is death".
But though it is blunt and to the point, it's also funny and sometimes cheesy with hints of Dredd's black humour coming through.
Urban rates his collaboration with Garland - the author of The Beach and screenplay writer for Danny Boyle's 28 Days Later - as one of the most rewarding experiences he's had in his acting career.
"The good directors and writers are the ones who are open to other people's suggestions. They don't get hung up on the fact it's not their idea and they will embrace it. I've been blessed to work with quite a few like that," he says, also referring to director JJ Abrams' Star Trek in which he played Bones McCoy.
But in stark contrast to the earnest and sometimes comic role of Bones, Judge Dredd is a pure action hero.
The Dredd 3D story - which Urban and its producers hope will evolve into a series of films - sees Dredd and his rookie, psychic sidekick Judge Anderson (played by Olivia Thirlby) having to bring down ruthless and demented drug lord Ma-Ma (played by Lena Headey, best known from Terminator: The Sarah Connor Chronicles and as devious Queen Cersei Lannister in Game of Thrones). As well as controlling the majority of Mega-City One's Slo-Mo drug supply - which users puff as if they are using an asthma inhaler - her stronghold is the 200-story Peach Trees building, a kind of tower block-meets-shopping mall which is home to more than 200,000 inhabitants.
Most of the action takes place inside Peach Trees and the single-set location recalls excellent Indonesian martial arts film The Raid from last year; only Dredd has more shoot 'em up action and a higher body count.
"It's a bit of a blast from the past in some ways, but then there's this whole new visceral style and energy that it's filled with," says Urban.
"So tonally we're quite different from the comic. It's a hard gritty look at that world. It's rough around the edges with lots of concrete. It's not polished corridors and sleek opening doors. And I like that about it. I think the designers honed in on the concept of a society that is really struggling to hold it together. I'm just really really happy with how it's turned out."
The actor, who divides his time between Auckland, Los Angeles and wherever his work takes him (for Dredd he was in South Africa for three months), downplays it as his biggest role to date.
"It's a big deal for me simply because of the fact I'm taking on a character that means a lot to me," he says, sounding very much like the blunt and calculating lawman of Mega-City One might do.
No matter what he thinks, after 20 years in the business, which have seen him go from TV shows such as Shortland Street, Hercules and Xena, to prominent roles in Lord of the Rings, Star Trek and as assassin Kirill in The Bourne Supremacy, Dredd is a coup.
He laughs when TimeOut suggests he could set up a one-stop shop at fanboy conventions, especially given he got to keep both his Dredd and LOTR helmets.
"I've got a bit of a collection going on," he chuckles.
He revelled in the research he did in the lead-up to developing Dredd's imposing on-screen presence and his harsh and raspy voice which he modelled on "a saw cutting through bone".
"Part of my research was to get hold of every single Dredd comic that I could," he says excitedly. "So I got to go back and have a look at all the really cool comics I loved as a teenager and also discovered a whole lot of new stories that had been written subsequently that I wasn't privy too - and it was interesting to see the evolution of the characters and the maturity of the writing."
Of course, portraying Dredd was made more challenging by the fact he wears a helmet - revealing just his chin and mouth - for the entire film. But he does the tough, upside down smile and staunch jaw well.
"It was a huge challenge. But what I discovered was, simply this, if you feel the emotion then you have to have faith that the audience will too because it does, somehow, come across, and it's reflected in your body language. But also, how you physically approach the action becomes very important and the voice also becomes very important because Dredd certainly uses his voice as a weapon at times."
For Urban, the key to the success of the character was to try to bring out his human side rather than simply playing an iconic comic book hero.
"To play the man, and that's it. He's one of those heroes who doesn't have super-powers, he has an extraordinary skill set, a cool gun, and a cool bike. He is the guy who is walking into the building when everyone else is rushing out in terror, which is what defines his heroism."
- TimeOut
