Helen Mirren’s flinty performance as Elizabeth II is getting all the attention, but equally impressive is Peter Morgan’s insightful script for this UK drama, which quietly teases out the social, political, and historical implications of the 1997 death of Diana, Princess of Wales. Shortly after the shocking news reaches Britain, Prime Minister Tony Blair (Michael Sheen) scores a PR coup by memorializing Diana as the “people’s princess,” while the royal family’s obstinate silence angers their grieving subjects. But Blair is more sympathetic to Elizabeth than many of his staffers, and he instinctively understands what she cannot: that in the tabloid age, celebrities are dangerously usurping the monarch’s hold on the public imagination. Stephen Frears directed; with James Cromwell and Sylvia Sims. PG-13, 97 min. a Century 12 and CineArts 6, Landmark’s Century Centre, River East 21.