LONDON — The University of London’s stolid Senate House echoes with secrets and hidden history — it was headquarters for Britain’s propaganda and censorship department and “1984” author George Orwell used it as a model for his Ministry of Truth — so it was a fitting workplace last July for Christopher Nolan and the masked ambitions of “The Dark Knight Rises.”

“Back in Gotham, back in Chris Nolan’s city,” actor Morgan Freeman said as he stepped past barbed wire and debris used in a just-finished scene. A moment later, he added: “The only drawback is this is the last one we get to work on with him. And a lot of us won’t really get that until later. It’s not until the curtain goes down that you think, ‘Jesus, that’s the last one.’”

“The Dark Knight Rises,” which arrives in theaters July 20, is, by all accounts, the last caped crusade for star Christian Bale and Nolan’s now-familiar ensemble of Freeman, Gary Oldman and Michael Caine. They’re joined by an infusion of “Inception” cast members — Tom Hardy, Marion Cotillard and Joseph Gordon-Levitt all appeared in Nolan’s perception-bending 2010 heist film — as well as Anne Hathaway.

The plot and the production have been treated like state secrets, which speaks to Nolan’s now-notorious practice of message management as well as his yearning for old-fashioned movie mystique in an over-information age. The 41-year-old filmmaker is defiantly old school — not only did Warner Bros. fail in a push to close out the franchise with a 3-D release (as “Harry Potter” did) but here in the digital summer of 2012 the Batman movie is the only major popcorn project that was shot on film stock.

Early on in the project, while still in Los Angeles, Nolan said this film’s introduction of a masked, hulking terrorist called Bane (Hardy) and the enigmatic Selina Kyle (Hathaway) sets the stage for an “appropriate conclusion” for Bruce Wayne’s odyssey as a vigilante sent into the shadows by the childhood sight of his parents’ bodies bleeding in the street.

“Without getting into specifics, the key thing that makes the third film a great possibility for us is that we want to finish our story,” the filmmaker said of the script he co-wrote with his brother Jonathan Nolan. “And in viewing it as the finishing of a story rather than infinitely blowing up the balloon and expanding the story … unlike the comics, these things don’t go on forever in film and viewing it as a story with an end is useful.”

“Rises” closes the grim trilogy that opened in 2005 with “Batman Begins” and delivered a pop-culture landmark in 2008 with “The Dark Knight,” the only superhero film to win an Academy Award in an acting category and the only one to reach the billion-dollar mark in worldwide box office. The Oscar remains a bittersweet achievement (the late Heath Ledger’s family accepted the award posthumously), and the box-office total is now just part of the challenge for a veteran cast and crew that must live up to its past heroics.

Special effects supervisor Chris Corbould has had plenty of stops in his career — he’s worked on a dozen James Bond films and picked up his first Oscar for the spinning successes of “Inception” — but the intensity and duration of the Gotham City work lent it the feel of an epic quest.

“I’d say it’s probably similar to the [crew] experience they had on ‘The Lord of the Rings’ trilogy,” said Courbold. “It’s a journey we’ve all been on with Chris; [‘Batman Begins’ was] his first action film and then with the second we made one of the most successful action films of all time. And with the third we hope to make the most successful action film of all time. It’s been a mission and it is a mission.”

There was a six-month shoot that included stops in Glasgow, New York , Newark, N.J., and Pittsburgh (where the NFL’s Steelers provided their stadium and some star players to film a game-day sequence for the Gotham Rogues) and the production was badgered by curious eyes and covert cameras. The Nolans have responded by clamping down even more on every aspect of the project’s public life.

“Chris likes his secrets,” Bale said, “and he keeps an air of mystery about his scripts and his plans. And I like that. He does it for a reason and it’s worked and the people who work on his projects know that this is the way we do it.”

Every tidbit of information has been dissected and debated by fans, especially in regards to the newcomers. Entire essays have been written about the big-picture possibilities of Gotham cop John Blake (Levitt) and Miranda Tate (Cotillard) and they may actually be on the right track; again and again on the set those characters were conspicuously avoided conversation topics.
 

There has been great consternation too, about the voice of Hardy in preview footage — Bane has a Caribbean-tinged accent and, with his respirator mask, many fans and bloggers have said the dialogue veered into a mechanical garble. Nolan says it’s a non-issue and, last summer at Senate House, producer Emma Thomas flashed a confident smile when asked about Hardy’s work.

“Bane is a really interesting match-up for Batman just in the physical strength and brute force he brings,” Thomas said of the dark mastermind who, in the pages of DC Comics, famously broke Batman’s back in a landmark 1990s story arc. “Tom’s preparation has been amazing and he’s transformed his body and found these great approaches to the character.”

As far as superhero films, the fevered fascination surrounding “The Dark Knight Rises” can only be compared to the global curiosity that greeted Tim Burton’s 1989 “Batman,” which starred Michael Keaton as the heroand Jack Nicholson as the Joker. Adding to the intrigue, this summer also has “The Avengers” and “The Amazing Spider-Man” to add new fuel to the half-century rivalry between DC and Marvel, the superhero equivalent of Beatles vs. Stones.

Truly, though, for the Gotham City crowd the only rival that matters is their own past. Even Bale, an actor of austere intensity who has a low tolerance for Hollywood hype, said there’s been a special aura about this project since Day One.

“I remember when I first read the script, of course it was all top secret,” Bale said during a break in the shoot. “I went round by Chris’ house, was shut in the room with the script — not allowed to leave with it — and it hit me that this was the last one. What Chris couldn’t believe was how slow I read because I go back and re-read until I have it all in my mind. I was in there six or seven hours. It was dark when I came out. And I was smiling.”

– Geoff Boucher