In a Paris primary school, a class of eight-year-olds sit behind their desks, eyes squeezed shut, counting to 20. At the back of the room their teacher, Antoinette (Laure Calamy), is getting undressed, slipping into silk frock for the school concert. “It’s not too much?” she asks the pupils. She’s having an affair with one of the dads – he’s married. Thus, with unparalleled Frenchness, begins this easygoing, warm comedy following Antoinette as she accidentally-on-purpose goes on the same donkey-trekking holiday as her lover’s family. As Antoinette bonds with her donkey, the movie evolves from gentle farce to journey of emotional growth. You might call it Eat Bray, Love – except it’s European, so there’s less pseudo-spiritual self-discovery and more drunken snogging.

Antoinette is meant to be spending the first week of summer holidays alone with lover Vladimir (Benjamin Lavernhe) while his family are at the beach. Instead, when his wife surprises him with a family hiking holiday, Antoinette impulsively books herself a place, too: six days of 20km hikes, staying in hostels. She arrives in teeny denim hot pants and huge wedge sandals – there’s as much Bridget Jones in her DNA as Julia Roberts. But Vladimir is nowhere to be seen, and, predictably, it’s not love at first sight with her stubborn donkey Patrick either.

There are some subtly pointed scenes at the beginning of the trek as a succession of guys mansplain to Antoinette how to manage her donkey. “Show him who’s boss,” says one handing her a whip. Instead, she uses her empathetic teaching style to win the beast over – and Calamy really grounds the movie with her funny, generous performance. The showdown with Vladimir and his wife, when it finally comes, is a lesson in the famous French casualness about infidelity. But Antoinette’s affair slips into insignificance quite quickly; the real chemistry here is with the four-legged ass, not the human one.

• Released on 5 March on Curzon Home Cinema.