Imagine Tom Sawyer and Huckleberry Finn making a movie in 1970’s England. Add a touch of Peter Pan, “The Goonies,” and Sylvester Stallone and you begin to get the idea behind “Son of Rambow,” a completely adorable film about two young boys who are so dazzled by Stallone’s “Rambo” that they decide to make their own sequel. Based in part on the childhood of writer/director Garth Jennings, it is a completely charming love letter to movies, to childhood, and most of all to the power of imagination and the pleasure of story-telling. I spoke to Jennings and his long-time colleague and producer, Nick Goldsmith.

I’d like to start with how you found these marvelous young actors.

GJ: The kids are amazing and they’re the reason that it worked. It’s hard to find good young child actors. These had never acted or done anything before. It took us five months to find them. It was an instant decision when we found them. They were both self-confident but not arrogant, and just thought it would be fun to do. Putting them together was like a blind date. But kids find it easier to form friendships than adults. We got them together and made a short film with them in my back garden for them to meet us and each other. We knew from that day we were all going to get on.

The second day of the shoot we had to film the beginning and the end of the movie. I wondered how easy it would be for Will (Poulter, who plays Lee Carter) to show emotion. It was glorious. They had the best time. They spent their whole school holiday being action heroes in movies.

How did you first begin to work together?

NG: We met at art college in 1990 or 91. We took this art foundation course, when you get to try out all the different forms of art. It was the best year you’ll ever have, experimenting with everything. We both ended up doing graphic design, then started making music videos. It was three years before we set up as a proper company. We started writing film scripts, eight years ago.

GJ: I started making films when I was 11 and the first one I ever made was inspired by “First Blood. Rambo was so self-sufficient, so exciting; he sews up his own wounds and takes on 200 men. It was everything you ever wanted from a film. It was the beginning of my liking making movies.

What was it like to adapt that experience into a screenplay?

GJ: As we worked on it, it was clear we had to add more dramatic structure. Making Will a kid who was so isolated from media and giving both of the boys some family issues gave the story more momentum.

NG: It had a feel-good factor, one of those films where you go out with a smile on your face, just feeling good about something.

One thing I especially loved in the film is that from the very beginning you get this sense of confidence that the boys are protected by the power of their imagination and passion. We know they are going to take all kinds of crazy risks but they are going to be fine.

GJ: That is how we felt about the memories of that time.

NG: You don’t know that it’s going to cause you harm.

GJ: We made it just a bit over the top so that people say, “Ah,” where you look back and say “That shouldn’t have worked.” But it did.

NG: We both had similar experiences, that complete lack of fear for consequences.

GJ: There is one very indulgent joke, when Lee Carter says, “We’re losing light,” as a professional director would, even though he could not have known that. But you can sort of get away with it. When you’re a kid you try to speak like the grown-ups do. They’re always saying things that are slightly too big for them.

Another highlight of the film is the French foreign exchange student, Didier.

GJ: Again, that is a slightly heightened version of our real experience. He is an amalgamation of all of our French exchange student experiences. We all grew up being part of a French exchange program. We both remembered them being these exotic creatures that would step off the bus and looked older than us and had great clothes that fit them perfectly, the boys our age always had a little moustache and seemed so much older and more sophisticated. But his character was so big that it was very easy to get carried away. We had to make sure not to let him dominate the story. He had to serve the friendship of the two boys. He showed them something all movie-makers learn — what happens when you get a star on board. It was nice to get something in that we knew about!

Was it a challenge to deal with the conflicts created by the very restrictive religious beliefs of Will’s family in the context of a light film like this one?

GJ: I grew up next door to a Plymouth Brethren family and the kids went to my school. My wife’s uncle teaches at a Plymouth Brethren school. A number of former members have written books and done interviews.

NG: In our story it was initially very peripheral. We are not trying to make a comment on religion. We wanted to get across on film what it feels like to see a film like “First Blood” for the first time for a creative kid. To give it to someone who has never seen anything before gives us a chance to show the impact. We are not belittling the religion. It was an amazing tool for us because it gave him everything he needed to have in order to change.

GJ: It creates a lovely dynamic between the two, one streetwise and and one religious.

NG: The religion is not the issue, the guy (one of the church leaders) is not right.

What are you working on next?

NG: Our next project is a jingle for a biscuit advert. And we’re writing animated film. We haven’t done that before.

GJ: We really loved making “Hitchhiker’s Guide to the Galaxy” but have no intention of ever doing it again. It’s like a great wedding day, fantastic, but never need to do it again. We don’t want to do another children starring movie but who knows?