They are pantomime horses, but not as we know them. Audiences are more likely to weep in empathy with these than laugh at them: from the timid colt awkwardly ambling across the stage to the great burdened beasts of war that snort, stamp and whinny, or die in agony.

The second season of War Horse, the National Theatre’s inspired production of Michael Morpurgo’s children’s story, is playing to sell-out houses. In March, as reluctant to give up the ghost as its horse hero, the show will move to the New London Theatre in Drury Lane. Originally the author thought “they must be mad” to try to make a play from his best-selling 1982 novel. But Nick Stafford’s adaptation and the miraculous skills of a South African puppeteer company have changed his mind and that of Britain’s theatre-going public, adults and children alike.

War Horse has proved another cross-platform success for Morpurgo, who has emerged as one of the country’s most respected authors for younger readers, leading - more by accident than design - a fightback against the glut of JK Rowling-style fantasy. There are no broomstick-riding witches flying around the world of Morpurgo, but he has cast a spell over generations of children with 110 books filled with what they and his adult fans acclaim as “magical storytelling”, not afraid to tackle the real world with all its horrors and wonders.

War Horse tells the story of Joey, first seen as a yearling colt, who is sold to the cavalry in the first world war. It shows the horrors faced by animals in war until Albert, the farmer’s boy who first rode Joey, comes to his rescue. The horses are brought vividly to life on stage by puppeteers, clearly visible beneath horse bodies of cane and stretched georgette, from the South African Handspring Puppet company of Adrian Kohler and Basil Jones. The puppeteers, who carry 60lb harnesses worn like backpacks, need regular physiotherapy. One confessed to feeling “knackered” after a performance, perhaps an unfortunate choice of word from someone playing the front end of a horse. Morpurgo, however, would see the knacker’s yard as one of the facts of life that children should be told about.

Thirty years ago, he and his wife, Clare, founded the Farms for City Children charity, which has arranged for more than 60,000 youngsters from deprived inner-city backgrounds to spend a week on a rural farm. These are places where children from the streets of, say, south London can learn that a tree is not just a tree - “there are different types” - and see where their food comes from. Morpurgo also thinks that seeing birth and death means they won’t be afraid “when grandfather dies”.

His books are filled with animals interacting with humans, from The Last Wolf (set in Scotland during the Highland clearances), via The Butterfly Lion to his most recent book, This Morning I Met a Whale. This arises from the story of the whale that captivated the nation when it swam up the Thames in 2006. Morpurgo’s Thames whale has come to warn mankind, through his young hero, that it is destroying the Earth; but it dies in the attempt.

The former children’s laureate believes that modern children, although more affluent than any previous generation, are also more isolated, withdrawing to their bedrooms to live in a “virtual world” with their laptops and televisions. He deplores the fact that many grow up with few books - or none - in the home. For Morpurgo, childhood is the critical, precious, fleeting time in which almost all the qualities that make up the future adult are created.

He thinks modern mothers go off to work when their children are too young, sending them to nursery as toddlers and to primary school at the age of four or five, younger than in many other European countries. Children are bombarded from birth with the “toxic effect” of marketing, he complains, while the government sees them only as future earners.

“Education is there to serve the needs of the children. Education is not there to serve the aims of government,” insisted this former teacher. He believes all trainee teachers should be compelled to take a course in children’s literature and that by Year 6 - when they are aged 10-11 - children should have a dossier detailing all their creative work: in music, drama, writing and art.

Morpurgo’s own childhood was anything but straightforward. His grandfather was a poet and philosopher whose house “groaned with books”, yet young Michael, not very bright at school, was more intimidated than inspired by them. Nor were his parents totally conventional, suffering what he calls “domestic collateral damage” from the second world war. Both were actors. After his father went off to fight, his mother took up with someone else. Michael was born in 1943. On his return from war, father exited stage left to Canada - leaving mother with two little children. Michael and his brother were brought up in the family of their stepfather, Jack Morpurgo, along with his two children.

Michael knew none of this until one Christmas when the family was watching a BBC adaptation of Great Expectations. At the point where the evil-looking convict Magwitch emerges from behind a gravestone, his mother shouted: “Oh, my God, that’s your father.”

Morpurgo was in his twenties when he at last met his father in person. They got on famously, man to man, without the barrier of the father having brought up the son. Morpurgo’s early childhood was in no way traumatic, however: his mother read to him nightly from Kipling or Edward Lear: “An early memory of an adult reading to you is powerful. With the story the link between the two of you, the words spoken with love, the intensity of that moment, it starts you on the most amazing journey.”

That other corollary of middle-class life, boarding school, was not so happy. Young Michael went to King’s, Canterbury, where he enjoyed the rich musical culture but hated the academic focus and rigid social life. He performed better on the rugby field than in the classroom but did not mix well and found himself “often climbing trees on my own”. He went to Sandhurst to become an army officer but was forced to leave through injury and got married at what he describes today - despite 44 years together - as the “ridiculously early age of 19” to Clare Lane, daughter of Allen Lane, the founder of Penguin books.

They rented a small thatched cottage on the outskirts of a Kent village and he taught for a year while trying his hand at story-writing - “doodling at it”, he says now - with no intention of taking it up. They were “mad on Shakespeare”, naming everything they possessed after his characters: a dog called Puck, two cats called Snug and Bottom and - eventually - three children, who ended up as Sebastian, Horatio and Rosalind.

After taking a degree in English and French at King’s College London, he went back into teaching and found reading to his classes for the last half-hour each day was one of the few things that kept their attention: “I could see there was magic in it for them and there was magic in it for me.” One day Clare suggested he try reading them one of his own stories. It worked, although Clare’s critical faculties were not wholly to be relied on. She admitted that, as a child, “my father gave me The Hobbit to read, but I didn’t like it much”. That was how Penguin missed out on JRR Tolkien, one of the titans of 20th-century literature. It was Clare’s inheritance from her father that enabled them to set up Farms for Children before Michael made money in his own right.

Morpurgo’s own influences were Robert Louis Stevenson’s Treasure Island, Ernest Hemingway’s The Old Man and the Sea, Paul Gallico’s The Snow Goose and Ted Hughes’s Poetry in the Making, which he heard on BBC Schools Radio as a young teacher. It gave him - and his class - a feeling of empowerment, a sense that anyone could go out there and do it.

After moving to Devon, to the thatched house where he and Clare have lived for the past 30 years, a looming apparition came up from the bank of the River Torridge towards him one day. It was Hughes himself. They became firm friends. Hughes famously took Morpurgo out when War Horse was short-listed for the Whitbread prize in 1982 but failed to win and told him it was “books, not prizes” that mattered.

War Horse was inspired by a chance meeting in Morpurgo’s local pub, The Duke of York, with a veteran of the Devon Yeomanry Horse Regiment, who told him horrific tales about animals wandering between the trenches and being used indiscriminately by either side. The stories were backed up by contemporary pictures he found in Allen Lane’s old trunk. Painted by FW Read, they showed horses “tangled, really horribly tangled” in barbed wire.

The immense audience reaction to the play at the National will be gratifying for an author who believes the traditional British distrust of emotion and sentiment is psychologically damaging. He believes books should “not satisfy you like chocolate” but should make people, particularly young people, ask questions. And that, far from disliking history, children can be fascinated by it when it is done well - so that fantasy comes second best.