Claire Denis’s Both Sides of the Blade, starring Juliette Binoche, joins other classics where three’s a crowd, from The Piano to The Favourite

Call it the original triangle of sadness. As much as the mores and taboos of screen romance have shifted over the decades, the love triangle has remained a constant: a problem that screenwriters rarely manage to solve without someone being hurt or worse. Ménage à trois solutions are rare; heteronormative coupledom must usually prevail. And yet our fascination endures with the simultaneously simple and wildly complicated crisis of loving two people at once – rarely depicted with more adult candour than in Claire Denis’s new drama Both Sides of the Blade, now streaming on Mubi.