IT is a book that has touched the hearts of millions of children, and now Michael Morpurgo’s acclaimed War Horse is being made into a film by top producer Steven Spielberg.

Among the cast of the film, telling the story of a horse caught up in the carnage of the First World War, will be actors including Jeremy Irvine, David Thewlis, Emily Watson, David Kross (who co-starred with Kate Winslet in The Reader) and Benedict Cumberbatch, who won praise for this year’s BBC adaptation of Sherlock Holmes.

The film is due to be released next year, but before then author Michael Morpurgo will be coming to Dorset to take part in the Poole Literary Festival, of which he is patron.

War and survival are frequent themes in books by the author who, as a child born in 1943, was evacuated to the country during the Second World War.

His parents – both actors – separated and Michael and his brother were brought up to be part of the family of his stepfather, Jack Morpurgo.

“I knew my father was an actor, but, because he left when I was about two, and divorce in those days was a shameful thing, we didn’t talk about it,” he said.

“What was hidden thereafter was that there had ever been another father on the scene. This was the Morpurgo family, and he simply wasn’t mentioned, and my mother didn’t talk about him.

“So he became a secret phantom father, and the first time I saw him was when he appeared on a Canadian Broadcasting adaptation of Dickens’ Great Expectations one Christmas Eve.

“He reared up on screen as Magwitch, the convict… and reared up into our household.”

That pivotal moment, which happened when Michael was 19, influenced him a lot.

“I write quite a lot about fathers who aren’t there, or grandfathers who turn up out of the blue,” he said.

“I’m connected with that world of a father I didn’t have. Who knows how wounded we are by such things?

“It’s a strange story that gets stranger as I grow older.”

As a boy, Michael loved reading comics and stories that moved fast. He liked Enid Blyton tales but realised “there wasn’t much meat there to get your teeth into” and you just wanted to know what was going to happen.

The first book he read and “really knew there was something different going on” was Treasure Island by Robert Louis Stevenson, who spent some years living in Bournemouth.

“Long John Silver was a wonderfully complex villain, and so attractive to a small boy,” he recalled. “And Jim Hawkins was the first hero I really identified with.

“I knew it was a great book then, and I think it’s one of the great books now.”

Curiously, Stevenson later had an influence on how Michael wrote his books. He had become a primary school teacher after university and enjoyed the classroom, particularly reading out stories: “I began to realise that children recognised the power of a story and, if you read it as if you meant it, it worked.”

One day he was reading out loud to the class a book that was boring, and the children were just looking out of the windows. That evening his wife, Clare, suggested he tell them a story instead.

So he did, and the class loved it… giving him the confidence that he could be a storyteller.

On the headteacher’s advice, he sent his stories to a publisher and soon after became a full-time published writer.

Today he writes longhand in exercise books in the “teahouse” in his Devon garden away from distractions like phones and where there is a bed on which he settles comfortably.

In the early days of his writing career he used to type, but found it increasingly painful. His friend, the late poet Ted Hughes, recommended standing and writing by hand, leaning on a lectern. But that too, proved uncomfortable.

And then one day he saw an old photo of Robert Louis Stevenson lying on a bed, propped up on pillows with an exercise book resting on his knees. He had a go – and has never looked back.

Today Michael Morpurgo has written more than 120 books, including modern classics like Private Peaceful, Why the Whales Came, The Wreck of the Zanzibar, The Elephant in the Garden, The Butterfly Lion and Kensuke’s Kingdom, His themes often centre on relationships between children and animals, which he believes may be partly because of the Farms for City Children project that he and his wife have been involved with for 30 years. Every year about 1,000 children from cities come to each of three farms to work for a week.

“It’s a privilege to see children and animals working closely together,” said Michael, whose books do not shy away from tearjerking issues.

“One thing I’ve learnt is that’s what holds attention more than anything else,” he said.

“Humour’s one thing – we can have a good giggle, and that’s fine – but it passes pretty quickly. And excitement only engages at one level.

“I think what really engages people is involvement in the lives of others. And the lives of others become the life of yourself as you’re reading it.

“You give of yourself and become deeply engaged with the emotions of the character and what that character is living through.”

War is the theme of Michael Morpurgo’s latest book, Shadow, released later this month (September 30, Harper Collins £12.99).

It’s the story of Aman, a boy fleeing the horrors of the Afghan war, whose life becomes linked to a dog that will not leave his side.

Meanwhile, Michael Morpurgo prepares for his visit to Poole to the Literary Festival where a production of Farm Boy – his sequel to War Horse – will be performed in the Lighthouse on Sunday October 31, where he will later join with the acapella trio, Coope Boyes and Simpson, to perform a concert version of Private Peaceful.

Then, next year, like the rest of us, he will be awaiting, with eager anticipation, the premiere of Spielberg’s film version of War Horse.

“I’ve been on the set and he just seems to have an unerring talent for finding the right people to play the right characters,” he said.

“I’ve huge confidence he will do something amazing with the film, just as the National Theatre have done with the play.”

• The Echo-backed Poole Literary Festival takes place from October 29 to 31 with 50 events featuring 30 writers including Deborah Moggach, Mavid Cheek, Poet Laureate Carol Anne Duffy, Beverley Naidoo, Katie Fforde and Minette Walters. For more details check out poolelitfest.com