There have been two major poet-directors this century: Jean Cocteau (who was born before the Lumiere brothers patented their cinematographe and died just as the French New Wave was coming in) and Pier Paolo Pasolini (who began life as a poet writing in an obsolete Italian dialect and died the victim of a gay-bashing on the coast near Rome).
Andrei Tarkovsky, too, though not strictly speaking a poet, is always seen as a director with a highly developed poetical sense, interested in what he calls "the poetry of memory".
In fact, Tarkovsky's father was a reasonably well-known poet in Russia, and films such as Mirror and Nostalgia are studded with quotations from his poetry about the Volga forests and immortality. But Tarkovsky thought that literary elements should not be self-evident in a film; indeed, using a metaphor rich in personal association (the making of a bell in Andrei Rublev is symbolic of all artistic endeavour), he insists that all poetry should be smelted into the whole.
Tony Harrison also uses a smelting image in his movie, when the god Hermes oversees the creation of a huge gold statue of Prometheus in a German foundry, adding the sacrificial bodies of a dozen striking Yorkshire miners in order to temper the metal. But Harrison is an polemicist of the old school and there's no smelting down of his dogged, two-line couplets in Prometheus.
It's been suggested that Harrison has invented a new cinematic form, where poetry is the engine that drives the film. The poetry is up-front and unabashed, not skulking in the wings as Tarkovsky intended. Cocteau would have approved. Like Harrison, Cocteau always considered himself first and foremost a poet and a writer. His interest in cinema was pretty much that of the dilettante. It was merely one of several forms he might use.
"I am not a cineast," he wrote. "I am a poet who uses the camera as a suitable vehicle for allowing us all to dream the same dream."
But Harrison is wary of claiming kinship with the wilting lily of Cocteau. He prefers the bracingMarxist-Freudian barrackings of that great neglected genius, Pasolini.
"To make films is to be a poet," is the Pasolini quote that heads the printed script of Prometheus.
"Pasolini was a poet before he was anything else," insists Harrison. "He is one of the best modern Italian poets, quite aside from his films."
In an intriguing mirror image to Tarkovsky's father/ poetry obsession, it seems that Pasolini began writing as a poet as an act of defiance against his own father, who was an army officer and an enthusiastic Fascist. In 1942 he dedicated his first book of poems to his father; the poems, eccentrically written in his mother's native dialect, were inimical to his father's political views because "Fascism is hostile to dialects" (Pasolini's words).
But Pasolini's interest in dialect was only part of the picture, part ofhis journey towards being a world-class director.
"Stylistically, I am a pasticheur," he told an interviewer in 1968. "I use the most disparate stylistic material - dialect poetry, decadent poetry, certain attempts at Socialist poetry."
It was this interest in politics that led Pasolini to poetry and then away from it - that and being in Rome (and broke) after the publication of his first novel. He started hammering out scripts to pay the rent.
Poets have never been as successful as novelists at turning their hands to the donkey-work of script-writing; they also tend to find the lack of control over the final product intolerable. They chase chimeras and exhalations, something a lunching producer would never understand.
"I'm often asked to write scripts for money," says Harrison. "But I never do - poets don't make merchandise, they make gifts."
Tarkovsky is scathing about poets prostituting themselves for what Cocteau calls "the seventh art".
"I do not understand why anyone with literary talent should ever want to be a scriptwriter," he pronounces in his memoir, Sculpting in Time - forgetful, perhaps, of the shining example of the French poet Jacques Prevert. Prevert was a poet whose scripts from the mid-Thirties exerted a huge influence on the poetic realism of Carne and Renoir, and in 1945 he received an Oscar nomination for Les Enfants du Paradis, still regarded as the greatest French film.
WH Auden, John Betjeman and Dylan Thomas all contributed to film projects but never showed any great interest in exploring the nuts and bolts of cinema.
Novelists tend to have better instincts and fewer scruples on the subject of commercialism: the cross-fertilisation between films and novels is now commonplace. William Boyd has recently finished his first directing job and Ian McEwan is considering following suit.
Poets worry people in the same way that undertakers do. But if their intimacy with language isn't allowed to get in their way, there's no reason why poets shouldn't sit in a director's chair - if they can, just for a while, forget that they are poets. To paraphrase Keats on the subject of poetry, it had better come to film as naturally as leaves to a tree - or it had better not come at all.