Yes (15)

A tirelessly non-conformist presence in British cinema since the Seventies, Potter is an unashamed intellectual and polymath: director, writer, composer and dancer, even the star of her 1997 film The Tango Lesson. She's also very much the thinking sensualist and romantic, with an eye to visual splendour and emotional rapture, notably in her version of Virginia Woolf's time-travelling Orlando.

Potter's most completely conceived feature to date, Yes is a formal dare, but it's also a love story, an essay on cultural difference and an attempt to grapple - as British film-makers rarely do - with the state of the world. Joan Allen's heroine, identified in the credits as "She", is a scientist, American although she identifies herself as Irish, having spent her childhood in Belfast. "She" endures a now-loveless marriage to Anthony (Sam Neill), a dry, philandering Englishman, with whom she shares an elegantly antiseptic home - white and spotless, though not as spotless as all that, according to their cleaner, the film's chorus figure. Played by Shirley Henderson, the cleaner assures us, in knowingly winsome asides, that there's no such thing as clean. Dirt - dead skin, love's stains, germs and all - represents the flux and force of life, and it's clearly a little bit of that gritty flux that She could do with.

She finds it in "He" (Simon Abkarian), a Lebanese surgeon working as a chef in a London restaurant: he loves to talk romantically dirty to her ("Lovely goddess, whore and tramp"), getting her hot under the collar and under the bistro table. Their affair is idyllic at first, but when He is sacked following an argument with a racist co-worker, the couple's cultural differences rise to the surface, and they confront each other in the film's centrepiece scene: She, as He reminds her, has her ideas about what it means to have a lover from an Islamic background, while He unburdens his own preconceptions about her identity as a Western scientist, a married woman and an American, rebuking her for the West's ignorance of his culture: "From Elvis to Eminem, Warhol's art/ I know your stories and your songs by heart - /Do you know mine?"

Delivered with realistic naturalness and jaunty rhythmic verve, Potter's verse works as a strict yet flexible structuring device, rather than as a mere conceit. While verse narrative has very occasionally been attempted in film (notably in Tony Harrison's awkwardly visionary Prometheus), textually Yes reminded me of Vikram Seth's verse novel The Golden Gate, which used detached Popeian wryness to offset the mundane language of modern lifestyle. At times, Yes errs on the side of polemical overstatement, as characters speak for the positions they represent; yet, because they always argue, challenging each other's definitions of themselves, the speakers remain fully-fleshed people and the film sustains a dialogue with its own passionately cherished contradictions.

Yes's analytical argumentation gains breathing space from the elegance and energy of the film-making, especially of Alexei Rodionov's photography, with its rich, polished play with textures (although there's appalling overuse of rapturously slurred slow motion). The acting is richly nuanced, the cast rising eagerly to the project's challenging strangeness. Joan Allen, not always the most approachable performer, is compelling here, as her polar facial surfaces melt in amorous rapture, while the charismatic Abkarian is at once macho seducer and jovial wag, knowingly playing off the Eastern stereotypes that She, against her better judgement, can't help seeing in Him. There's also some terrific support playing, notably Gary Lewis, Wil Johnson and Raymond Waring, as the "rude mechanicals" of the piece, Abkarian's fellow kitchen hands, while Sam Neill's pained, ironic dryness makes a perfect fit for the verse.

The show-stopper, though, is Sheila Hancock, as She's dying aunt: speaking in voice-over, while she lies eyes closed in a hospital bed, Hancock delivers the valedictory of a lifelong Communist who still holds to one enduring ideal ("Cuba" and "Castro" are her dying "Rosebud" words), and whose last wish is for the world to grieve, loudly and boisterously, at her passing. A fine, sly performance of a moving passage, Hancock's turn highlights the essentially operatic nature of this non-sung film, her deathbed "aria" bringing a dash of irreverence to undercut Yes's overall tendency to earnestness.

Yes might not immediately speak to current tastes. As its Joycean title suggests, it's anti-cynical, almost militantly affirmative, and it makes no bones about taking film, and the world, seriously. It may ultimately be a film to admire rather than love or thrill to, but it's a real achievement by one of Britain's few out-and-out, all-round auteurs (Potter also wrote her own original score, with old left-field campaigner Fred Frith). Whatever you make of Yes, there's no denying it raises the bar for audacity in British film. Potter's peers should take on the challenge, although they can stick to prose if they prefer.

j.romney@independent.co.uk