"The seed we had collected was for a strain of wheat that had long been thought to be extinct," he explains. "It was a strain that is resistant to sunn pest, which decimates wheat crops worldwide. The value of that seed," Street says, shaking his head, "is absolutely incalculable for all mankind."

Street is known as the Indiana Jones of the agricultural world. For the past 10 years he has worked for the Syrian-based International Centre for Agricultural Research in the Dry Areas (ICARDA), scouring the world for ancient seeds, the genes of which could be used to save the world from a catastrophic food shortage.

"Collecting and storing seeds is of paramount importance for our survival. As city people we have become so disconnected from how we get food on the table."

Shot on location in Central Asia, the documentary Seed Hunter follows Street and his small team as they search remote fields. Information is sketchy, maps unreliable and the weather harsh. But the goal, as always, is seeds, the more rare the better.

"ICARDA's Syrian seed bank now holds 135,000 seeds across 10 different crop species," he explains. "The idea is to capture as much variation as possible within a given species. This is because, when the crops we are currently farming fail, we can use these seed variations to breed a new, more resistant crop."

Climate change is having a devastating impact on harvests in Australia, where once high-yielding crops fail year after year. "Even our best, most heat-resistant crops won't be good enough to cope with the lowest forecasted temperature rises," Street says. "If we can breed a wheat that can grow with less water, using the genes from our seed bank, it will literally mean the difference between people starving or not."