ET the Extra Terrestrial Christmas Eve 3.40pm BBC1

The grand plans of Steven Spielberg came to fruition in 1982 with ET the Extra Terrestrial, the film which he had always seemed on the verge of making. Melissa Matheson's screenplay taps into the essence of childhood, and of Spielberg. It's a story of wish-fulfilment and the perfect, unattainable friendship - a sort of Before Sunrise for kids.

The young Henry Thomas, who has eyes as big and bright as buttons, plays Elliott, into whose life and garden strays a walking Yorkshire pudding. Accidentally left behind on earth by his mothership, which had presumably paused to stop at a Welcome Break service station on its trip home, the creature's fate rests in the boy's hands. Luckily, Elliott is not the sort of urchin who plucks the wings off of dragonflies; a friendship blossoms, based on learning and trust and, most crucially, affairs which are beyond the understanding of adults.

Spielberg wants access to youth's secrets. (The film toys with two childhood preoccupations: imaginary friends and fear of abandonment.) But nostalgia can taste stale on celluloid. So why does ET feel so fresh? Because of the playing - Thomas (and an itsy-bitsy Drew Barrymore as his quacking sister) have a spontaneity that has usually been beaten out of children by the time they are shoved in front of a movie camera.

More than that, ET amounts to an artist pitching everything he's got into the dark, at his audience. That's something that few directors are fearless enough to do. Spielberg lost his nerve thereafter. He sought refuge in the mechanically thrilling Indiana Jones trilogy, a smattering of self-consciously sombre projects (of which only Schindler's List succeeded) and Always and Hook, the most wretched follies known to mankind. He will never make a film as purely cinematic, or emotionally raw, as ET. Which is only one of a thousand reasons to cherish it. Did I mention that it's the greatest weepie known to terrestrial, and extra-terrestrial, civilisation?