With access to the real players, and using extensive, dramatic reconstruction Supergrass illuminates twelve crime ridden years in a world that seems far off Britain now, but is actually near-history. A world where the policing rules were very different, it explores the strangely ordered rules of the underworld where Supergrasses were the only way to crack the gangs, who were causing havoc in seventies ‘Sweeney’ London. A London where guns were used in armed robberies every week, and the city felt like the Wild West. The film tells the stories of dramatic crimes and outrageous criminal characters. People like London’s biggest bank robber and the first supergrass in 1972, Bertie Smalls, and Maurice O Mahoney, armed robber and hard man who shopped hundreds of associates in 1976.