'Don't miss the climax,' runs the advertising slogan for the final part of the infamous cinematic trilogy derived from the books by EL James. But breathless narrative twists were never the selling point; the climax, when it comes, is yet more of the fumbled plotting that has made the Fifty Shades films a trial to watch.

Fifty Shades Darker ended with a memorable image: a photograph of tycoon Christian Grey (Jamie Dornan) with his face dissolving as the red-hot cinders of an aggressively-positioned cigarette burn through the paper. There's nothing so striking to observe in this final part, in which Grey and new bride Ana (Dakota Johnson) wrestle with married life; only jealousy, possessiveness and knife-wielding stalkers stand between them and domestic bliss. There's not even a whodunnit to be solved, as the mysterious Mr Hyde (Eric Johnson) has been identified as the culprit. The real question is why does he hate Ana and Christian so much?

As the series draws to a close, it's increasingly easy to see where Hyde is coming from – most of the audience will learn to loathe Ana and Christian too. Endlessly flaunting their unearned wealth, speaking in nonsensical code, dressing like catalogue models and displaying all the personality of department store mannequins, the central couple provide a hollow centre for this tedious drama, which rolls back its supposedly daring exterior to reveal a heart of dull conservatism.

The profit-margins don't lie though, and financial considerations must have made it worthwhile for Johnson, Dornan and Fifty Shades Freed director James Foley to remain faithful to the franchise. But professional reputations should suffer, since the only people getting satisfaction from this closer are those with a stake in its success. For the creative talent, the Fifty Shades experience may have turned out to be more punishment than pleasure.

General release from Fri 9 Feb.