Bringing his stepfather’s books to the big screen has been quite an adventure for Douglas Gresham. At the recent royal premiere of The Chronicles of Narnia: The Voyage Of The Dawn Treader, Mr Gresham met the Queen, who reportedly shed tears during a poignant scene at the end of the film.

It seems neither the Royal Family nor the public are showing any sign of Narnia exhaustion as the latest in the film series, based on the third of C.S. Lewis’s seven books, arrives in the cinemas for Christmas.

Mr Gresham, pictured, 65, certainly isn’t. “I’ve lived in Narnia all my life,” he tells me. “And I’ve no intention of ever leaving it.”

Narnia has been central to Mr Gresham’s own story ever since he arrived in Oxford in 1953, a little American boy aged eight, accompanied by his brother and mother, the poet and novelist Joy Davidman.

She would become the wife of C.S. Lewis, with the story of their short time together before her death from cancer the subject of the play Shadowlands and later the Richard Attenborough film.

Mr Gresham spent a key part of his childhood at The Kilns, the home in Risinghurst shared by C.S. Lewis and brother Warnie. For when Joy died in 1960, Mr Gresham and his brother continued to live with the Oxford University don, until C.S. Lewis’s own death in 1963.

When he had first met Jack, as C.S. Lewis was known to family and friends, Mr Gresham was disappointed.

“I suppose after being taken with his books, I half expected a man on speaking terms with King Peter and Aslan to be wearing armour and a sword belt, rather than a slightly stooped, balding figure dressed in shabby clothes.”

But Lewis would show him the woods and lakes behind The Kilns, and teach him to look for fauns and dryads among the sycamores and beeches. And the great author would read to him from his Narnia books.

“Jack taught me to read. I don’t mean read as one learns in primary school, but to read for the love of reading and learning.”

Even as a boy, Mr Gresham recalls thinking about how the Narnia books could be turned into films. But it would be almost half a century before his dream was realised with the release of The Lion, the Witch and the Wardrobe five years ago, which became the highest-grossing live action film in Disney company history.

Mr Gresham, who now lives in Malta, has played a central part in bringing all three Narnia films to the big screen, having co-produced the first two, and being credited as executive producer of The Voyage of the Dawn Treader.

“In a way I have been involved with the Narnia books from the time that my mother married C.S. Lewis. I always wanted to see the books turned into movies. But it has taken time for the technology to reach the stage where a film could do justice to them.”

He recalls proposals during Lewis’s life time to make an animated version of The Lion, the Witch and the Wardrobe.

“He was always worried about someone doing a cartoon and making Aslan look ridiculous. That was something he just did not want to happen.”

After studying agriculture and working as a farmer in Australia, Mr Gresham found work as a broadcaster. Working on the periphery of showbusiness and film, he believes, gave him some early understanding of how film-making worked.

He was to gain further experience acting as a consultant for the film Shadowlands, with Anthony Hopkins playing C.S. Lewis.

He recalls a deeply moving scene where Hopkins and the actor playing him as a boy break down together in shared grief.

“It had been put into the script. The strange thing is that it actually happened. It was the only time it did. When it came to emotions we were terribly English.”

As a result of his work with the C.S. Lewis Company, which is responsible for handling Lewis's estate, first as director and later as creative consultant, Mr Gresham persevered for almost two decades to find a film production company that would to bring The Chronicles of Narnia faithfully to life on the big screen. He finally chose Walden Media.

As a devout Christian, he readily recalls having prayed for guidance before signing the agreement. He says he has never regretted the decision.

“The new film,” he says “is much less limited because we are now travelling from one country to another and from island to island. I think the sets in this film top everything we have ever done.

“We all embark in this world on a life. And that life is represented in the book by the Dawn Treader.

“It is the story of how you get from the beginning to the end, with all the trials, difficulties and temptations that may beset us on the way.

“So I think there is very much a spiritual motif.”

He remains hopeful that more Narnia films will follow, while insisting everything will depend on the success of the new film.

Mr Gresham loves to recall speaking to a group of Rotarians about one of the earlier films and being asked by one member of the audience: “How did you train the lion?”

He has no doubt that C.S. Lewis would have approved of the films, particularly “the fantastically beautiful lion”.

For him, the world still has the wrong picture of C.S. Lewis.

“There is this idea that Jack was a dour scholar locked up in Magdalen College.

“He was, in fact, a man full of life and a great raconteur. He was a man who had grown up with the thinking of the 19th century and believed in honesty, personal responsibility, commitment, duty and courage.”

One of the myths comes down to Lewis’s own pen.

“Not good with children,” he said of himself.

But Mr Gresham recalls: “I have never met a man who was better with children. And I have never met a man so considerate to women.”

One of the saddest passages in Mr Gresham’s book on his childhood in Oxford, Lenten Lands, written a decade ago, recalls his return to The Kilns following Warnie’s death.

“I found that it was empty,” he wrote, “sacked as thoroughly as if by a band of Viking marauders. Everything was gone.”

The surrounding land had been sold to property developers.

“Where once lovely trees had stood, now stand maisonettes and thus are memories of childhood swept away.”

Still, at least Narnia survived both for him and millions eagerly awaiting the arrival of the three-dimensional Dawn Treader.