Gypsy Blood started as a long-term photographic project by Leo Maguire four years ago. "I started this project in 2007 originally as a documentary photo story," says Maguire. "I had written an overambitious proposal on documenting the world of gypsy bare-knuckle fighting and applied for the Getty Grant [for Editorial Photography] way back in 2007. Unfortunately for me I got the grant - you apply for these things but never imagine winning them. I was given nine months to complete the story. I can't even begin to explain how tough it was to try and gain access to this closed-off community. Patience and gentle persistence began to open doors but it has been a long and arduous process."

But in 2010 Maguire started shooting video using the Canon EOS 5D Mk II camera. "I felt that the people, the situations, just had too much texture for stills to fully capture and convey to an audience but I didn't know what to do with the footage; I thought perhaps some form of multimedia," he says. Eventually he showed some rushes to a professional film editor, who "was amazed at what I had and convinced me I should shoot a documentary film," which received a commission for More4, a British cable network, in early 2011.

"When I originally set out to make the film, I was attracted by the violence of my two main characters, who are strong macho men. Their kids were kind of too young to make much of an impression on me, two or three years ago," he says. But, over the last seven months, Maguire has been spending a lot more time with his subjects. "That's when I started to see that the kids are the real characters. Their fathers tell their kids these stories about fights. And the kids are just in awe of this. They soak it up like a sponge."

Living with these families, Maguire built up a connection with one of the kids. "The film effectively takes you on this journey with him and you hope that he will be able to stay a child a bit longer. But, by the end of the film, you see him die as a child metaphorically and become a gypsy man."

The film was originally commissioned by More 4, but when Anna Miralis, the commissioning editor, viewed the first cut she was so taken with the film that she offered for Channel 4 to show it instead. Gypsy Blood was the launch program for True Stories with its move from More 4 to its new home on Channel 4. "The highest viewing figures for a True Stories film on More 4 was Catfish with 700,000 viewers, we always hoped Gypsy Blood would beat this figure, of course with it being shown on Channel 4 we had potentially a much larger audience."

In fact, 2.5 million people watch Maguire's documentary on 19 January.