War Dogs is based upon a 2011 Rolling Stone article titled The Stoner Arms Dealers written by Guy Lawson, and follows two arms dealers Efraim Diveroli (Jonah Hill) and David Packouz (Miles Teller) who receive a government contract to supply weapons for U.S. troops in Afghanistan. Bradley has a small, yet pivotal, role as a shady gun-runner Henry Girard in the flick, which sees him re-team with The Hangover director Todd. And when working on Henry’s characterisation, Todd reveals that he immediately decided he wanted to see him in glasses similar to the ones worn by American serial killer Jeffrey Dahmer.

“I said, ‘We need these glasses. Forget who's under the glasses. Ignore that. But look at Jeffrey Dahmer's glasses,’” he told Den of Geek. “I wanted him to wear these glasses with the really heavy prescription, and Bradley wrote back, ‘Let's do it.’”

The key element of costuming proved challenging for Bradley though, as the glasses strained his eyes throughout the entirety of the shoot. But in the end, the 41-year-old actor chose to play up the fact that his eyes tend to get a little red normally in order to achieve his character’s bloodshot look.

“He's staring through these glasses all day long, and he has the worst headache by the end of the day, because you can't fake that prescription. So he's looking through, basically, a legally blind prescription. His eyes are all big and weird, so it throws him off a little,” explained Todd.

The Due Date helmer also shared that while the film has strong echoes of the original article, parts of the narrative are dramatised and the character of Henry is entirely fictionalised. But Todd feels the creative licence is justifiable in this instance.

“He's a bit of an amalgamation of two characters. I mean, you do that sometimes in a movie - it's the economy of storytelling, you know,” he said.

War Dogs is currently showing in U.S. cinemas and opens in the U.K. on Friday (26Aug16).