The John Lewis Christmas TV ad has come early and it’s a nightmare. Domhnall Gleeson and Margot Robbie put on fraightfully upmarket English accents and stand around like tailor’s dummies in this bizarrely clenched and infantilised tragedy-twee heritage drama about AA Milne’s fraught relationship with his son Christopher Robin.

The poor, bewildered little moppet got roped into the Winnie the Pooh publicity machine as the books’ popularity exploded in the 1920s. Will Tilston plays the eight-year-old CR, while Alex Lawther – on the verge of typecasting, I fear – plays the unhappier older teen version, bullied at his boarding school. Famed author Milne had served in the trenches during the first world war, and had suffered from PTSD, or shell shock as it was then known; he vowed to give up his comic fripperies and write a serious anti-war tome. But then, well, as all the world knows, he was inspired to write the Winnie the Pooh books, and forgot about grownup stuff for the time being.

Well, good for him of course; he did more for world happiness and world peace with Winnie the Pooh. But the film feels the need to approach his great creation in the appropriate mood of joyless anaemic solemnity, a mood that intensifies as the second world war approaches.

The first word of the title signals the movie’s weird misery imperative. Kelly Macdonald sorrowingly plays nanny/housekeeper Nou, without whom poor old AA can’t make his boy a proper breakfast and winds up serving lumpy, bland porridge. We know how that tastes.

