Charles Causley, who celebrates his 80th birthday today in the small Cornish town where he has lived all his life, tells the story with diffident pride and amusement. "In the midst of all this guff, it's very important not to take yourself too seriously. I don't think Shakespeare did," he says, with gently rounded Cornish vowels. It sounds like a defence from a man to whom critics have not always been kind. His work, though popular, has never been trendy. "I expect I shall be hammered," he says, anticipating criticism of the new Collected Works published to celebrate his birthday.
Although he is most famous as a poet for children, his Collected Poems shows a more serious side. He once shared a platform at the Edinburgh Festival with W H Auden ("It was wonderful for me, I don't know what it was like for Auden"), claims to be the only living writer mentioned in Iona and Peter Opie's writings on children's language and has had the expatriate Cornish community weeping at readings around the world.
His friend and West Country neighbour, Ted Hughes, says: "Among the English poetry of the last half century, Charles Causley's could well turn out to be the best-loved and most needed." It is curious praise, "most needed". Yet Hughes may be right. There is something enormously satisfying in Causley's deceptively simple forms and tales of ordinary men, women and children in a difficult world. Their stories are nothing special - sad sailors, missing people, day-to-day adventures, chance encounters - yet they have the haunting power of folk legends and moral fables in which death is often near.
To Causley, life is tough. Driven by the guilt of the survivor, he writes often of the men who did not come back from the war as he did. The sea is a recurrent theme, but his is not a romantic vision of the ocean, rather terror at its destructive power. "It reminds me of David Copperfield speaking to Emily," he says. Emily tells the young Dickens hero how she is afraid of the sea: "I have seen it tear a boat as big as our house all to pieces."
Charles Causley was born in poverty in Launceston, Cornwall, in 1917. His father, a groom and gardener, died shortly after the end of the war and his mother worked all hours to survive. As a child, he dutifully attended church with his mother and the cadences of the King James Bible are inscribed on his subconscious. "Then, like Coriolanus, I began to see there were other worlds than this," he says. He discovered George Orwell and the New Statesman and found his heroes among local socialists and members of the Communist Party. When he left school at 15, he worked as an office boy, then in 1940 joined the Navy. He decided that if he survived the war he would train as a teacher, and, after six years at sea, he did so.
Sitting in the book-lined study of the modest house where he cared for his mother until her death, Causley claims he was not a good teacher. He says, though it is hard to believe, that he had too short a fuse when class sizes were as large as 45. But the experience left him with strong opinions about writing for children. Only when he has finished a poem will he decide who it is for, adult or child. The test is who will get the most out of it.
"To me, poems like Christopher Robin are absolutely sick-making," he says. "It's better that children read something than nothing, but it's not for me. I don't believe you should patronise children by writing silly, sickly verse." Teaching was a great experience, he says. "They know all about betrayal, birth, death, marital infidelity. You should respect the child and never offer them mush."
That does not mean all verse should be serious, however. Some of his own best poetry has a comic bathos and among his favourite poets is the nonsense writer Edward Lear, to whom he unveiled a plaque in Poet's Corner at Westminster Abbey. Breaking into the plaintive "Calico Pie", Causley says: "Children can see the sadness that lies in poems like that. You can see the effect on them. It's terrific."
Charles Causley always wanted to be a writer, even when he was the little boy who always had his essays read out by teacher. Before the war, the BBC broadcast a couple of his plays and his first poem was accepted by a magazine while he was in the Navy. The magazine folded without his poem seeing publication, but he says that did not matter. "I thought, my God, I think I can do it."
He considers writing both a gift and a skilled job. "I knew that I had a gift for words and if you've got a gift of any sort you should exercise it. It's a kind of betrayal if you don't. Never despair, you must keep going."
You can see why some describe him as a Christian poet, though it is as much social and moral justice - or injustice - that drives him on. He is not at all sentimental, but a poem like "Timothy Winters", about "a blitz of a boy" with a drunken father and runaway mother, burns with a quiet indignation. "Timothy Winters has bloody feet / And he lives in a house on Suez Street, / He sleeps in a sack on the kitchen floor / And they say there aren't boys like him any more."
Yet while Causley speaks animatedly of his socialist heroes, angrily of how the Jews were betrayed in the Thirties and sadly of the children he taught who stood little chance of further advancement, he appears loath to nail his personal colours too firmly to any mast. In the poem "Cornwall", he speaks of a day when "the granite beast will rise". At a time of nationalist fervour, does he feel himself a Cornish poet? "Oh, I think that's just about a place I live," he says, seeming unwilling to risk offence.
Throughout his work, there are references to the streets and alleys of his native town. Dockacre, Ridgegrove Hill, Zigzag, the strong Norman castle that looks out upon the "cardiograph of granite" which is Dartmoor, all are instantly recognisable to the residents of Launceston. Most have lived there all their lives, too. He has known them since their schooldays and asks after them. They, in return, note how he looks frailer these days than the handsome upright fellow they remember.
He claims he could leave, despite the ties, yet it seems unlikely now. He had a stroke a few years ago and does less driving than he did. Though he has travelled widely since he first sailed with the Navy to Gibraltar, he says inspiration is always unexpected and may lie just around the corner. "You might think, what was there growing up in Launceston in the Twenties? There was the silent cinema! Charlie Chaplin in black and white films - absolutely magical." He draws an analogy with the paintings of Christopher Wood which he saw recently at the Tate Gallery in St Ives. "He kind of moved the scenery around a bit, they were not exactly as he saw things," he says. "I think that's what you have to do with a poem."
Peculiarly, for a man resolutely practical, who accepts growing old - "You can't stop the clock" - and who won't use a typewriter "because it makes the poetry look too good too soon", Charles Causley is also adamant there is something "unexplained" about life. But after a moment of otherworldliness, he returns to the present. "I used to think, when I was young, that poetry was away and somewhere else," he says. "But it isn't. It's under your nose. You just have to use your senses. There's nothing special about the experiences, but not everybody values them."
! Collected Poems 1951-1997 (pounds 20) and Selected Poems for Children (pounds 5.99), published by Macmillan on 5 September.