By Jayne Nelson

When Bethan Roberts wrote the novel My Policeman in 2012, her story was based, loosely, on a real-life love triangle: author EM Forster’s relationship with a married police officer, and the effect it had on the man’s unsuspecting wife. But her book – and by extension, this film – also functions as a history lesson.

My Policeman details the shocking hatred directed towards homosexuals in 1950s Britain, an era in which being ‘outed’ could result in a prison sentence. By casting former One Direction heart-throb Harry Styles as the lead, director Michael Grandage has found a canny way to draw in and educate new generations about our shameful history.

The story opens in the sleepy seaside town of Peacehaven in the 1990s. Marion (Gina McKee) receives a bedridden invalid into her gloomy home, becoming his carer despite the unspecified objections of her husband, Tom (Linus Roache). Robbed of speech by a stroke, the patient, Patrick (Rupert Everett), seems angry and uncomfortable.

It’s all very mysterious: why is he there? Marion doesn’t seem to like him much. Worse, Tom refuses to even look at their visitor; instead, he spends hours away from the house, furiously walking his dog. (Kudos goes to Roache for somehow making ‘strolling by the sea’ look like a declaration of war.)

The answers lie in the past. We leave the claustrophobic, dreary house to flash back to colourful Brighton in 1957. Emma Corrin – who played Princess Diana in The Crown, with the same doe-eyed vulnerability on display here – is the younger Marion. She’s dating a dashing policeman named Tom (Harry Styles, trying his best but out of his depth). Marion is in love, but is confused about how Tom feels in return: does he like her or not?

Tom then introduces her to his friend Patrick (David Dawson), a museum curator who’s been educating him in the joys of art and culture. As Patrick becomes a huge part of their lives, Marion starts to sense that perhaps the two men are closer than is prudent. It’s a feeling that worsens when she eventually marries Tom, but Patrick still insinuates himself into their lives – even taking her husband on a trip to Venice, alone.

Back in the ’90s, the older Marion finds Patrick’s diaries from that era and we get confirmation that he and Tom were indeed in love. Their sex scenes are handled delicately by both the script and the director, but this section focusing solely on the men is also where the film starts to come undone.

Dawson is excellent as the refined, worldly Patrick, but Styles’ acting skills simply aren’t on the same level. It’s most noticeable when he’s forced to play ‘drunk’… the downfall of many an accomplished actor, let alone a man still learning his craft. As a result, what should be a sensitive, passionate love story between two characters occasionally lacks conviction.