The Lost City of Z: New Behind-the-Scenes Images Venture into Jungle, Battlefield

Charlie Hunnam (left) and director James Gray on the set

Before Charlie Hunnam was cast in the role of Percy Fawcett in The Lost City of Z (opens in limited release April 14), Benedict Cumberbatch was in line to play the part. When Cumberbatch's wife became pregnant with a due date in the middle of the jungle shoot, director James Gray decided to move on with the project instead of waiting for the actor to fulfill his Doctor Strange obligations. That was when the film's production company, Plan B, made a recommendation. "Plan B again called me up and said, 'What do you think of Charlie Hunnam?' I said, 'He's terrific, but I don't want to cast him because I want an English actor for this part,'" Gray recalled. "They said, 'Well, what are you talking about? He's from Newcastle.' I didn't know he was English because I had only seen him on Sons of Anarchy, where he's doing an American accent, so I didn't know he was English."

Charlie Hunnam (left) and director James Gray discuss one of the battle scenes

And the partnership worked out. "When I met him, I thought he was fantastic for it because he has a real dashing quality to him, almost like Errol Flynn would have had in the 1930s," Gray said. "But he's also very dedicated and willing to convey doubt. He has danger. Jax has danger in Sons of Anarchy. I was interested in mining both his swashbuckler side, but also that level of danger, the uncertainty that goes along with who he is."

Robert Pattinson (left) and director James Gray discuss a scene on the set

Gray was originally drawn to the film both for the complexity of the project and its protagonist. "What draws me to a character is not necessarily what draws everybody else to a character," Gray said. "It's a very specific, personal thing to you, but what I found captivating about him was that he had both an internal struggle and an external struggle. He was a heroic figure, but not a flawless figure, a very complicated and complex person. What drove him was ambition and, of course, the desire to rectify the family's shame. But at the same time, there is something beautiful about his pursuit. It's not only a selfish one. It's also routed in some kind of history. When you're talking about that kind of complex motive, which is both heroic and filled with a personal and intimate complexity."

Director James Gray (left) discusses a scene with actress Sienna Miller

"I read David Grann's book and thought that this is going to be the most difficult movie of all time to mount, both to get made and actually the physical act of making it, I don't even know if I'm going to be able to get this done," Gray said. "After thinking that, it was the thing that made me want to do it."

Director James Gray discusses a scene on the set

Once on set, Hunnam proved himself more than capable of filling the role. "He was so dedicated," Gray said. "It's tremendously rewarding to work with an actor who knows more about this entire thing than you do at the end. He knew everybody else's lines and lost 50 pounds in a matter of eight weeks for the part."

Robert Pattinson on the set

As rewarding as the film was for Gray, it's not likely he'll be shooting in the wild again any time soon. "It was about as difficult a shoot as you could possibly imagine," he said. "I'm thrilled that I did it, and I'll never do it again."

Director James Gray sets up a shot on the set

Director James Gray gives some instructions to the actors on the set

Crew and talent await the call of “Action” on the set

A smaller crew captures the action on the river during filming