For fans of action TV and martial arts cinema, "Gangs of London" is one of the greatest series of the modern era. Created by Matt Flannery and "The Raid" director Gareth Evans, series director Corin Hardy ("The Hallow," "The Nun") has crafted a high-octane gangland thriller with the kind of stunts you don't typically see on TV. Season 1 ended with the series' mysterious Investors achieving apparent victory in their efforts to eliminate Sean Wallace (Joe Cole), replace him as head of the...