My Policeman: Harry Styles’s bisexual bobby is far from arresting

Asking Harry Styles to star in films was someone’s bright idea ever since his Dunkirk cameo. An even better one would be encouraging him to act – especially if he’s to wade through tricky lead roles requiring shading he currently can’t handle. First there was his waxily robotic husband in Don’t Worry Darling, and now we’re stuck with his frustrating immaturity in My Policeman, the effortfully glum tale of a bisexual bobby in the homophobic 1950s.

Styles is the most jejune of six actors, who play out a tragic love triangle twice – first in 1957, when Tom (Styles) marries a teacher called Marion (Emma Corrin, in pained Diana mode) despite his secret affair with museum curator Patrick (David Dawson). Forty years later and no happier, the trio are played by Linus Roache, Gina McKee and Rupert Everett.

It’s tough for us to puzzle out why the older Patrick, who has suffered a stroke, has been taken into care by the married couple – or rather by Marion alone, since Tom wants no part of it. (Roache and Everett share almost literally zero screen time.) Is this Marion’s guilt? Someone’s punishment? A cogent adaptation of Bethan Roberts’s 2012 novel would put these confusions to bed, but Michael Grandage’s handling of Ron (Philadelphia) Nyswaner’s script leaves us in the dark.

All we know is that Tom and Patrick were furtively carrying on while Marion was little the wiser. The film gets bad laughs when the marriage is consummated: compared with the vigorous, unabashed sex Grandage has staged between the men, Styles is a ten-second wonder when he’s atop Corrin, whimpering apologetically to a finish.

Bisexuality is clearly not Tom’s forte. He angrily lies to Marion about Patrick, but she also shudders at the very concept of same-sex love. Their sham marriage is no great advert for the institution, but manages to make us flatly despise both parties in it.

Patrick is the only one, as they say, living his truth, despite striving through an era when he could easily be blackmailed, like Dirk Bogarde’s tormented barrister in Victim. Dawson’s sad-eyed performance, capturing that hunted quality while trying to be dashing in the circumstances, makes this one character ring true.

Grandage’s feature debut, the literary biopic Genius, was an all-star dud; this is colourless, miscast, adrift. He hasn’t yet found cinematic lift-off: the camera gazes endlessly into the soupy sea off Peacehaven, as if it were a Magic Eye picture hiding the drama of a Turner painting inside. Amid the drab ruin of these lives in the 1990s, and their equally cheerless salad days, rare sparks of life succumb to a great deal of mopey regret.

15 cert, 113 min. In cinemas from Friday October 21