When you’re watching a silent film and the whole audience gasps in horror and surprise at the same time, you know it’s not a museum piece you’re looking at. The First Born was released in 1928, just as Britain was first being seduced by those new-fangled “talkies”, but it has more than enough tricks up its sleeve to tempt moviegoers in any decade.

Chosen as this year’s Archive Gala for the London Film Festival, The First Born is a disarmingly frank story of sex and love among the aristo set, shot with precocious flair. Actor Miles Mander directs, and also plays the lead: a scoundrel of a baronet named Hugo Boycott, whose marriage is inevitably in crisis. Hugo and Maddie’s relationship runs hot and cold. One day they’re falling into each other’s arms, the next they’re having one of their rows – and real shoe-flinging, bag-packing, door-slamming humdingers they are too. Maddie (Madeleine Carroll) blames the arguments on her own jealousy, which is to say her pain at Hugo’s philandering. But there is another reason for the couple’s unhappiness: their childlessness. Whether this is anything more than the baronet’s old-fashioned desire for an heir is open to question, but Maddie certainly believes a baby will solve her marital woes. Hugo’s behaviour is fairly abominable at every turn, but his wife’s decision to deceive him in order to save their marriage provides the drama’s fatal twist.

And this is a complex story, with the truth about the Boycotts’ marriage and the outward appearance of it constantly at odds – a conflict that comes to the fore horribly when Hugo runs for parliament and a distraught Maddie is forced to stump for him at a public meeting. We can’t hear what Maddie is saying, and there are no intertitles to help us, just her pained expression, and superimposed cheers of encouragement from the crowd: “Good old missus!” They think she’s a sweetheart, Hugo thinks she’s a monster. Fans of The Graduate (1967) will note the speed with which their faces fall in the cab journey home. It’s delicately done, but it’s a heartbreaking moment.

The First Born is a wonderfully well directed film, in fact, eliciting a tremendous, anguished central performance from Carroll, and a sizzling one from her irresistibly dashing “noble admirer”, David (John Loder). Both actors, like Mander himself, went on to further success – Carroll most notably in The 39 Steps (1935) and The Secret Agent (1936), and Loder in another Hitchcock film, Sabotage (1936). Mander’s only venal directorial sin is vanity: he gives himself far too many lip-curling closeups, and risks turning Boycott into a pantomime villain. Mander’s performance is enjoyable, but it is not a tenth as sophisticated as his co-star’s. His virtue on the other hand, is his audacious use of camera movement, dissolves and overhead angles to disorient and excite the narrative. There’s one prowling handheld tracking shot that plunges the audience straight into the psyche of a suspicious husband, running his hands over ruffled bedsheets. Elsewhere, a sequence of dissolving closeups of Carroll and her manicurist Phoebe shows the transferral of one idea between two minds: a folie à deux in the making. We’re in the latter stages of the silent era here – Mander had made short sound films before but this was his debut feature – and The First Born is the work of a confident director on top of his material and with creativity to spare.

That’s not to say that he was not ably assisted. The screenplay for The First Born was co-written by Alma Reville, a woman with many years’ experience in the film business, but yes, better known to us now as the wife of Alfred Hitchcock. It’s tempting to credit her with some of the film’s sophisticated touches – from its elegant structure, to its sparse use of intertitles and the sensitive portrayal of Maddie as far more than just a wronged wife. The First Born is never afraid of emotional complexity, from the ambiguities of Maddie’s friendship with David, and her betrayal by a close friend, to a brisk montage of painfully contradictory telegrams.

The quality of the film should stand for itself, and those who have seen it at festivals over the years have long championed The First Born as a lost British classic. Critics at the time of its release thought it was a bit “sordid”, but they said pretty much the same thing about Pandora’s Box (1929), so there’s no reason that a film this accomplished, and entertaining, shouldn’t be embraced by a wider audience in the 21^st century. And that is why the BFI has showered so much love on it. We see it now in a more complete state than before – frames from a 16mm print found in the George Eastman House in New York have been spliced in where there were gaps in the BFI’s 35mm copy, reinstating an expression here, an exit there, to make the film a more smoothly satisfying experience. Cue marks, scratches and holes have been erased and the original, delicate tints restored. The film also now benefits from a fresh score – composed by Stephen Horne and performed live at the gala screening. It’s melodic, and elegant, but fantastically adept at ramping up the tension in the crucial moments. There’s a haunting theme, played on the oboe and underscored by percussion and piano, that seems to appear when Hugo’s own jealousy gets out of control; there’s a humorous use of the accordion when Maddie’s friend Nina raises a sardonic eyebrow; and a thunderous combination of piano keys and strings during an unexpected violent catastrophe.

The exquisite new score is the finishing touch in the rebirth of The First Born – a fascinating film, ripe for rediscovery.