It came as quite a surprise in 2003 when Disney put its $50m prized adaptation of The Hitchhiker's Guide To The Galaxy in the hands of Hammer & Tongs, the duo of director Garth Jennings and producer Nick Goldsmith who had made commercials and music promos but no features. The film went on to make more than $100m worldwide at the box office.

And now comes another surprise, as Hammer & Tongs follow up that commercial hit with a smaller, more personal story, Son Of Rambow, which premieres at Sundance on January 22.

The film is about two boys in 1980s England who are inspired by First Blood and other action films and decide to shoot their own movies. Jennings says the idea, if not the exact characters, is rooted in his own childhood. "I used to make strange movies with my strange little friends," he remembers. He says that Son Of Rambow is a "rose-tinted view" of childhood and recalls that "old-fashioned notion of growing up with a sense of mad ambition and enthusiasm".

The film sees the world through the eyes of children, as well as 1980s-style home movie out-takes, scenes from First Blood (Sylvester Stallone, Brian Dennehy and Richard Crenna's estate all liked the script) and some unusual illustrations and animation coupled with 1980s tunes and a gigantic orchestral score.

Director Jennings explains he had the idea for Rambow six years ago, and started developing it with the old incarnation of Film4. About three years ago, Hammer & Tongs got the script back and began developing it independently, pulling together financing and casting. That is when Hitchhiker's came along and they put the project on hold. "What we learned on the mechanics of film-making and storytelling tricks from Hitchhiker's have helped us," Jennings says.

After discussions with many potential partners, they met with Celluloid Dreams and the Paris-based company quickly came on board for production funding and international sales.

Son Of Rambow, with its eight-week shoot on a budget of $5.8m (£3m), was clearly shot as a leaner production than Hitchhiker's. "I like working in a commando-style unit," Jennings says, before adding with pride: "We didn't need a playback system or a monitor because there was nobody to see it but Nick and me."