Twenty years ago I used to wonder if Jon Stewart was ever going to come into his own. It was obvious he was brilliant, but TV didn’t have a format for his gifts. Some soon-cancelled chatshows, a couple of movies, a book, and the endless treadmill of the stand-up circuit: these were his lot. Turned out his perfect format was being worn by a jockish fratboy with a hip sportscaster’s shtick called Craig Kilborn: The Daily Show. Within a couple of years – particularly during the weeks-long Florida recount controversy of 2000, when he and his Daily Show reporters stopped shaving and washing, as if caught in some neverending seventh news-cycle of hell – Stewart had made the format his own.

As he coasts towards TDS retirement with the same gusto that alleged “lame duck” Barack Obama displayed at the White House Correspondents’ Dinner last weekend, spending night after night disgorging himself of his bottomless contempt for Fox News, Bill O’Reilly, CNN and Dick Cheney, Stewart is heading towards another period of fuzziness. What does such a figure do after manning the hottest seat on the late-night circuit for 16 years? Retire? Please, he’s 52. Become a grand old man of the news media? No. He insists that he’s a comedian and, anyway, you ought to see the punches he’s landed on “grand old men” such as Tom Brokaw and Dan Rather.

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For the time being, then, movie director doesn’t look like such a bad job choice. Certainly his debut Rosewater shows that his writing and direction skills are considerable and subtle. Based on the experiences of Maziar Bahari (Gael García Bernal), an Iranian Newsweek stringer based in London, during and after the 2009 Iranian election, Rosewater channels Kafka, Orwell and Koestler in its depiction of totalitarianism brought to bear on the helpless individual, yet also manages to find laughter among the horrors. Bahari’s father was jailed by the Shah in 1953, his sister by the Ayatollahs in 1980 and now it’s his turn, for broadcasting violent demonstrations against the Iranian state.

Bahari’s principal tormentor is a sexually repressed, career-minded interrogator nicknamed “Rosewater” (after the “perfume of the righteous” that he wears), played by Kim Bodnia. A measure of the film’s evenhandedness is the care it takes to make Rosewater a figure of some complexity: frustrated, broken, somehow worthy of our sympathy. In one scene, Bahari makes up erotic nonsense about massage parlours in New Jersey and, like some horny 1950s Catholic priest, Rosewater demands further details (“This could be very important…”).

Once Bahari has started to take the piss, he’s already secured his private victory. When he loses control and starts laughing hysterically at his antagonist, his triumph is complete. A very Jon Stewart conclusion, then: laughter is what will save us.