Campaigning drama tends towards the melodramatic. Characters are destroyed, not by their own flaws, but by outside forces.Common (July 6), by the estimable Jimmy McGovern, was a lovingly directed, consummately performed, thoroughly researched and rather moving 90-minute play. It was also a melodrama: its central character was as blameless as a flapper tied to a railway line.McGovern was campaigning against the law of “joint enterprise”, which allows people involved in a murder to be convicted without their having wielded the knife. Some panicky Liverpool kids ran from a fast-food takeaway to a waiting car: one had stabbed and killed a blameless onlooker while the others were intimidating an enemy. All were implicated. So, too, was the driver, Johnjo O’Shea, who kept the