Marriage is hell, divorce is heaven and breakdown is a purgatory in between. I Give It A Year, a London-set comedy, is as patchy as a troubled marriage, glum one moment and hysterical the next. Judged by the press show, it sorts those recognising and responding to its take on matrimony from those not. Silence in row A, happy uproar in row B, nervous giggles in row C ...

I loved Stephen Merchant's tactless, blue-joking wedding speaker who sends the party's cringe thermometer through the roof. Rafe Spall (boorishly extrovert while simultaneously little-boy-lost) and Rose Byrne (vulnerably sophisticated) are a match made in the world's worst match factory, crafted to strike a brief, flaring light, then sputter and fizzle. Anna Faris, sweet and pretty-plain, and Simon Baker, a smoothie made from forbidden fruits, are the interloper tempters.

There is a very funny malfunctioning threesome scene, illustrating the asymmetrical warfare of the DIY mini-orgy. (One person always gets dumped on the bedroom floor.) And writer-director Dan Mazer (Borat, Brüno) has an unsparing skill at pushing comic situations to the pain barrier and beyond. These include a relationship counsellor (Olivia Colman) whose own relationship, judged by her off-office screams down a phone line, needs all the counselling it can get.