Why does it sell still? Why is the movie so compelling, when book and picture - about a rogue architect, a genius, of course, fighting the mobocracy, and about a woman's eye gazing up at his phallic skyscraper - are no more than headstrong intellectual trash? The BFI may mean to be praising director King Vidor more than author Ayn Rand. But here they are, nearly 50 years later, pitching a movie that slaps you in the face with its nerve and tabloid immediacy. As it starts, we see an architectural drawing - Frank Lloyd Wrightish, a low-slung house, jutting into space. On the line, "Do you want to stand alone against the whole world?", we cut to the first of three identical shots. An upright figure blocks out the left edge of the frame - as strong as a load-bearing pillar - and on the right a seated figure looks up at the tall, silent man. In the first, we see a Dean of Architecture at some Ivy League school, who is expelling the man.

In the second, a fellow student, ingratiating yet furtive, tells the pillar to bend, to compromise And in the third, an old man seethes over the same drawing. He's troubled because he sees genius, or egotism, things he's been trying to forget So he tells the pillar to report for work next morning. "What's your name?"We cut to a new angle: the tall figure pauses at the door in a bare white room, marked only by a dark couch and shadow lines from a window frame. The figure is as austere as the decor; and though it is Gary Cooper, he says, "Howard Roark."The first line hammers in the theme of the picture, and every image is a brick towards its building.

The black-and-white photography (by Robert Burks) is harsh yet elevated; it's film noir as seen by Eisenstein or Gerard Manley Hopkins. As befits a film about architecture and the filling of space, The Fountainhead demands to be seen on a large screen. The opening is staccato and headlong, but it also gives a hint of omission - its gravity is utterly lacking in humour. This can account for audience mirth at the "absurd" situations, the mannered dialogue and the trance-like playing. The Fountainhead is one of the most remarkable films ever made in America. But it's also a bit like a Roark building - so daring, so extreme, it risks falling over.