In 1992 Quentin Tarentino gave us Reservoir Dogs. At a stroke he reinvented the gangster genre and turned it into a comedy of manners with a deadly undertow. This new mutation looked as if it might be easy to copy. Many tried. Among them was Jez Butterworth, whose 1995 play Mojo takes Tarantino’s zany-macabre format and moves it to Soho in the 1950s.