It's a cliché of screenplay development that a writer should take the best bits of their story, cram them into the first ten minutes, and then write eighty more with the same high quality. It worked for Jim Cummings, who wrote, directed and starred in his Thunder Road short, then reshot it as the opening of his first feature. Taking its name from the classic Bruce Springsteen song, Thunder Road has become a critical and commercial success that belies its tiny $190,000 budget, a fairy-tale success story.

'I absolutely never thought it would happen to me,' says Cummings on his promotional tour for Thunder Road. 'But I wouldn't have thought it was possible if I hadn't seen how the people who did Napoleon Dynamite, Whiplash, or even Saw managed to do it. I saw how they'd expanded their proof-of-concept shot films to become great features, so instead of waiting for someone to help me out, I just got started.'

In both versions of Thunder Road, uniformed cop Jim Arnaud (Cummings) stands up in church to talk about his dear departed mother, who ran a dance school. Distraught, the policeman unwisely decides to show his emotions through a choreographed dance set to Springsteen's music, the result horrifying the other mourners, and his own daughter. It's captured in a cringe-inducing long-take that's agonising to watch. And unfortunately for Arnaud, his lowest moment is being filmed on camera-phone…

'I love seeing the comedy of Alan Partridge or Mike Judge, it's not joke-based or about punch-lines, it's character comedy,' says Cummings. 'Also I loved Pixar films that made me laugh and cry at the same time, I wanted a film that was like a live action Pixar movie. Once I understood who Jim was, I wondered; how can we put him through heaven and hell? That's what Springsteen's music is about, he uses automotive metaphors to create redemption for characters suffering their own personal hell…

'I'd originally thought that the short film would have to be the climax of the feature, but that would have sucked. Then I was thinking about screenwriting structure, about this inciting incident you're meant to have on page ten, and I thought, what if the movie begins with this funeral-dance scene, and the whole movie is about him trying to persuade his daughter to love him again?'

Thunder Road is a deliberately small film, warm and gentle to its characters in the best tradition of indie film-making. Once Cummings had his opening scene nailed down, the rest of the story just fell into place.

'After that break-through, I spent five days hammering the first draft out in my friend's basement. We had to take Jim to his lowest point, and see him suffer; a police officer dancing at a funeral seems inappropriate to everyone who sees it, and the result is that this masculine guy feels that he can't be open about his emotions. The way social media works is, because of this one weird thing Jim did out of love for his mom, he might end up suffering for the rest of his life,' says Cummings. 'So I was able to use him as a tool to discuss lots of things, about the children of divorce, the education system, the justice system, inequality, race relations, mortality…I empathise with Jim Arnaud, he's like everyone from Job to Daniel Blake. He's a guy with a heart of gold who doesn't fit into the system, and I think that's a universal thing that people can relate to.'

Thunder Road is on general release from Fri 31 May.