A chance meeting and the anguish of unfulfilled passion

Desire in movies works best when it goes unfulfilled. The process of longing makes for much more engaging cinema than its resolution. Whether it's Gerard Depardieu's large snozzled Cyrano De Bergerac pining for Roxane, putting words into her suitor's mouth when he knows that he will never possess her himself, or Joan Fontaine pining for Louis Jourdain's rogue in Max Ophuls's Letter From An Unknown Woman, the most poignant love stories are those in which frustration and disappointment ultimately triumph.

"I wish, I wish," Laura Jesson (Celia Johnson) plaintively murmurs in her voice-over in Brief Encounter as she sits in a railway compartment, pining for Alec Harvey (Trevor Howard). Their relationship is impossible. She is a young, married mother with a young family and a bluff, dependable husband (Cyril Raymond). The idea that she could start a sexual relationship with another man in the prim, class-obsessed British society of the time was unthinkable.

In the 1960s, audiences used to find Brief Encounter ridiculous. In the so-called permissive era, Lean's depiction of a world in which characters listen to Rachmaninov music in lieu of having affairs seemed utterly bizarre. They mocked Celia Johnson's refined, cut-glass voice as she primly tells us: "I've fallen in love. I am an ordinary woman. I didn't realise that such violent things could happen to ordinary people." In Brief Encounter, the trains like the Rachmaninov music are used to denote the passion that the characters can't otherwise articulate. Lean isn't able to show Alec and Laura having sex (part of the point of the story is that they don't) but he can depict trains roaring into tunnels with steam billowing.

The closest physical contact between the would-be lovers comes when they first encounter one another. She has a tiny bit of grit in her eye. He as any good doctor would helps take it out. "That's how it all began," she recounts.

At one point, Laura and Alec almost do manage to consummate their relationship. However, when they go to a friend's flat, they are interrupted and Laura has to flee down the backstairs. This leads to one of the film's great scenes Celia Johnson running through the rain as Lean cranks up the Rachmaninov on the soundtrack. "I ran and ran until I couldn't run any longer... I felt so utterly humiliated, defeated and so dreadfully, dreadfully ashamed."

Even this scene is eclipsed by the lovers' parting at the railway station. They sit drinking tea, looking wretched. He has decided to go to Africa. It's the most momentous, heartbreaking event in Laura's life but it is rendered absurd when a busybody acquaintance blunders into the caf and "crashes into those last few precious minutes we had together".

The brilliance of this scene and of the film as a whole lies in the collision of the tragic and the banal. This story about unfulfilled desire unfolds against the backdrop of provincial English high streets and railway stations. Alec takes the 5.40pm train, leaving Laura's life for good. Even at this climactic point, she is forced to keep up appearances. However, thanks to the music, close-ups and voice-overs, we're in no doubt of the all-consuming anguish she feels at the desire that she now knows she will never be able to fulfil.