Karl Urban’s snarling, bestubbled lawman never does anything so impertinent as taking his helmet off: instead, in a plot thread burrowed from more than one Eastwood picture, not least Dirty Harry instalment The Enforcer, he mentors a rookie, murders hoods with the law’s full support and shows the city’s chief gang leader who’s boss by tossing her right hand man from a 70 storey balcony.