The Danish Girl is as purposefully constructed as its subject: Einar Wegener, a Danish landscape painter who was one of the first to go through sex reassignment surgery in 1930. Einar had been living as Lili Elbe for at least 20 years before that. Eddie Redmayne plays both parts, with Alicia Vikander as Gerda, Einar's wife, who supported him through the transition.

Tom Hooper needed seven years to get it made. When he first read the script by English playwright Lucinda Coxon, he didn't have the market power. An Oscar for best director for The King's Speech helped. Eddie Redmayne's Oscar for The Theory of Everything may have helped more.

Everything depends on Redmayne making Einar to Elbe not just believable, but sympathetic, even heroic. Hooper set out to make a film that would inspire the transgender community in their struggle, he says rather grandly in interviews. He cast 40 to 50 transgender actors in the movie, just not the one role that some in the trans community most wanted to see – a trans actor as Lili. To be fair, Lili has about one third of the screen time of Einar, so Redmayne's casting is not just defensible, but necessary.

Hooper's strategies as director are another matter. For a film with such an interesting tale, Hooper does his best to make it lifeless and 'artistic', slathering jam all over the toast. This is an exercise in constructed melodrama, galloping toward an unearned sense of tragedy, draped in fine fabrics. Einar and Gerda, first encountered in Copenhagen in 1926, are very much in love – young bohemians, hot for each other, six years after their marriage. Their apartment is stark like a theatre set, a soft grey, so as not to distract from the fabulousness of these two beautiful people. Quaint peasant women in folded bonnets made of newspaper sell fish on the quayside.

Einar is a successful painter, even if he seems only to paint the one tableau – a watery scene with four wintry trees. Gerda gets nowhere doing portraits, until the day she asks him to pose in a woman's stockings and shoes, so she can finish the leg of their ballerina friend Ulla (Amber Heard), who's late. Einar comes over all funny once he slips into stockings.

Hooper directs these scenes like a school play. Vikander and Redmayne appear ill-at-ease, overdoing the affectionate sexuality. There's no reality to their relationship: it's as if they are trying to seem wooden. It's only when she sees Lili, dressed for her first public outing, kissing another painter at the Artists' Ball, that conflict arises. Henrik (Ben Whishaw) presses his attentions. Redmayne debuts the set of cliches (eyes downcast, halting smile, general air of deer caught in headlights) that constitute his highly mannered performance. If you're getting the impression I don't see this as a turn worthy of its Oscar nomination, you'd be right.

Once the dressing up becomes a problem for the relationship, the movie is on firmer ground, because Vikander carries it there. Her loss of the man she loves really does seem tragic. It's more her movie than his, at least if we assume that penetrating the emotions of the character and engaging with their inner life is the aim.

Some of this is down to Coxon's script, which is based on a novel by American writer David Ebershoff. He fictionalised the real story of Gerda and Lili. Hooper says he brought some of the true story back, which is odd, given how far it strays from the little we know. Einar was probably homosexual before the marriage; Gerda lived as a lesbian when they settled in Paris in 1912. Her erotic art, none of which we see, was all lesbian, but that wouldn't do if we are to see her story as tragic, because of the 'loss' of her man. Nor was she by Lili's bedside for the last act, their marriage having been annulled already. We avoid also the details of the controversial surgery and the fact that the doctor was trying to implant a uterus. Is this decorum, or the need not to complicate the dramatic drive toward a weepy (and fictitious) conclusion?

The film is a lost opportunity, saddled with a kind of crushing formality. The metaphors fly about in the wind, whisking scarves into the air in risible moments of faux feeling. The frocks are more convincing than the emotions. Einar, Lili and Gerda deserved better.

Twitter @ptbyrnes