Pope Pius IX (Paolo Pierobon, excellent) has a smile that could freeze a chalice of communion wine at 20 paces. With a peevish curled lip and eyes as hard and sharp as the point of a knife blade, he’s a power-crazed pontiff who, according to this taut, factually based period drama by Marco Bellocchio, also happens to be borderline bonkers.

It’s at the pope’s behest that, in 1858, a six-year-old Jewish boy in Bologna, Edgardo Mortara, is seized from his parents. Allegedly, the boy was secretly baptised as a Christian by a former maid. Now, according to Catholic law, he is a Christian for eternity and cannot be raised in a Jewish household. Gaunt with grief, his parents petition for his return but meet the immovable wall of Catholic dogma and the will of an embattled, intractable Pius IX. With stately restraint, Bellocchio manages to put the audience in an ever-tightening chokehold of tension and outrage.

• In UK and Irish cinemas now and on Curzon Home Cinema