In “Son of Rambow,” the follow-up to their film version of Douglas Adams’ “The Hitchhiker’s Guide to the Galaxy,” the British team known as Hammer and Tongs (writer-director Garth Jennings and producer Mick Goldsmith) turn to a creation entirely their own—a story about two fatherless classmates in 1980s England who, despite their differences, become close friends when they collaborate on a wacky video sequel to Sylvester Stallone’s “First Blood.” The picture was a smash at this year’s Sundance Festival, where Paramount Vantage ponied up $8 million for distribution rights.

In Dallas for a showing of the movie at the AFI Film Festival, they duo said that it took fully eight years to get “Rambow” made. “The executives said that adults won’t go see film with children in it,” Jennings recalled, noting that even the success of “Billy Elliot” wouldn’t convince them otherwise. That’s why, Goldsmith added, “it’s been extremely rewarding to see it pay off. How it’s going now [in screenings] is even better.”

When asked why Rambo, Jennings said, “That came very much from my own experience. I was about twelve years old and I’d seen, I think it was a pirate copy of ‘First Blood,’ and it was the first film I’d ever seen that wasn’t meant for my age group. And I grew up on the edge of a huge forest. And now we saw a film about a man who could run around in the forest and take out two hundred soldiers just with a knife and a stick.

“We didn’t understand the whole idea of Vietnam—that went completely over our heads. All we saw was a man sewing up his own arm, having jumped off a cliff. There was a self-sufficiency that blew our minds. And also we were seeing something we shouldn’t. Quite soon after I made my first home movie based on that character, which I called ‘Aaron.’ That basically got me started making movies.” He added that “Son of Rambow” is “an affectionate homage to that movie. I didn’t want it to be a cheap joke at [Stallone’s] expense.”

Goldsmith added that that required setting the script in the 1980s, too. “It’s when we grew up,” he said simply. And Jennings added, “You draw on your own experiences, and then you realize you can’t transpose them to another time because they’re wrapped up in what was a much more innocent time for us. There were so many things from that era that were wrapped up in the story, we couldn’t move it.”

“But you don’t have to know about the eighties to enjoy the film,” Goldsmith added. “Kids have done this thing in different forms over the years—they do it now, developing a friendship through doing something. And maybe more important than that—what we’re trying to capture in the film—not having any fear of the consequences. If it works, it works. If it doesn’t someone breaks a leg. But it’s all right—it’ll get fixed. You’ll get through it. And I think that’s in a way what we were trying to capture, rather than making a story about the eighties.”

Another unusual aspect of “Son of Rambow” involves the fact that Will, the shy, sheltered boy, belongs to the religious group known as the Brethren, which secludes its youth from modern forms of entertainment. But too much shouldn’t be made of that, the filmmakers insisted.

“We needed to have a way to make the moment when Will Proudfoot sees ‘First Blood’ for the first time to have a really significant effect on him—for it to be like an epiphany, a real turning-point,” Goldsmith said. “I knew of [the Brethren],” Jennings added, “and they always struck me as very interesting.”

“It gave us that thing,” Goldsmith continued. “If you’ve got a kid who’s not allowed any form of entertainment in their life, it was great for us, because certainly seeing ‘First Blood’ was going to have a huge effect on him, especially if he’s got a creative thing about him, as Will does. So in simple terms it worked as a great device in creating conflict within the story.”

Jennings added, “It was as simple as that. We weren’t trying to make a comment about the Brethren or religion in general.”

He also noted how difficult “Son of Rambow” had been to cast. “It took us five months,” he said. “And it wasn’t until the very end that we found [the leads]. We found great kids along the way, but they just weren’t quite right. They didn’t match the characters we had in our minds.”

But then they found Will Poulter and Bill Milner. “They just had this natural charm, confident but without being stilted,” Jennings said. “They weren’t self-conscious, they were just very natural. And they became best friends making the film,” just like their characters did making theirs.

Asked whether they felt more or less pressure making this movie as opposed to an established fan favorite like “Hitchhiker’s Guide,” Goldsmith opined, “It’s a different kind of pressure—[‘Guide’] is Douglas Adams’, in a way, whereas ‘Son of Rambow’ is very personal, our story. It puts [more of ] the pressure on you [rather than him].”

To which Jennings simply added, “I concur.”