It is the place said to have inspired Narnia itself, such was its imposing beauty and serenity. It is difficult to believe such a thing now, looking in late November at the open land behind the house in Risinghurst that C.S. Lewis and his brother Warnie called home.

When the brothers first moved there in 1930, Warnie had described the garden as “such stuff as dreams are made of”.

Then it had been part of The Kilns estate, with paths carving through woodland and around Shelley’s Pond.

Since 1969, the land has been in the hands of what is now BBOWT but for those arriving in search of Narnia, the C.S. Lewis Community Nature Reserve can prove a disappointing experience.

The reserve was recently visited by Lewis’s stepson Douglas Gresham, whose mother Joy Davidman had married the Magdalen College don internationally known for his children’s books. He spent much of his boyhood playing in this place, talking with his stepfather and looking for fauns among the trees.

But after flying to England from Malta, where he now lives, his return to The Kilns 50 years after C.S. Lewis’s death proved both a sad and shocking experience.

“It seems to have been neglected. To me it looks shabby. You know, this was such a beautiful place one time,” said Mr Gresham, as I joined him on his emotional return to what is called “the real Narnia”.

“If you say you are going to maintain it, then you have to maintain it properly, otherwise you are just better leaving the place alone.”

He gestured towards beer cans floating in the lake. But the loss of trees caused him most upset. “They have chopped most of the larch trees down. I don’t understand why. Trees have been cut down and just left to rot. I think Jack [the name he knew his stepfather by] would have been a bit upset.”

Later in our visit he would bemoan the lack of fencing, the state of pathways, the number of fallen trees and the loss of bamboo trees that the Lewis brothers had themselves planted. The condition of an air raid shelter built at the beginning of the Second World War by the author and his gardener would also upset him.

“This is of real historic value. You could imagine Americans wanting to take this away and rebuild it somewhere else,” he pondered.

His hopes had not been high when he returned. In his book about his childhood, Lenten Lands, he had reflected on the changed appearance of his former home.

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

But he was to learn more development is beckoning when we returned to the house, where he had enjoyed so much of his boyhood The house, which is owned by the C.S. Lewis Foundation, now closely resembles how it would have looked when he lived there, following the death of his mother.

Within minutes of walking through the door he was being briefed about a plan from a near neighbour to build sheltered accommodation in his garden, necessitating an access road, running past the house and the nature park.

Jonathan Beecher, a musician, whose home borders the reserve, wants to put up two-storey accommodation units and music room.

Dr Deborah Higgens, director of the C.S. Lewis Foundation and resident warden of the house, feared it would damage the neighbourhood, while Mr Gresham declared “it would make a mockery” of what the Lewis house and grounds meant to people.

The 50th anniversary of Lewis’s death had already sparked debate about whether Oxford has made the most of the celebrated author and scholar.

While other towns and cities would have recognised the massive tourism potential from its links with the 20th-century’s best-known children’s book author, Oxford hardly makes life easy for C.S. Lewis devotees who manage to find The Kilns in the first place.

Extensive modernisation robbed The Kilns of much of its character.

Even the house’s setting has changed dramatically. When the brothers acquired it, it had been a house in the country, with grounds covering eight acres with just a few cottages and a farm as neighbours.

The Kilns estate was sold and in 1968 the Lewis Close cul-de-sac was built with further housing development along Kiln Lane.

The two brick kilns, after which the house was named, have long since disappeared.

Ronald Brind, a childhood friend of Mr Gresham, who was a regular visitor to the author’s home and went on to organise C.S. Lewis tours, has been a persistent critic of Oxford’s approach to Lewis.

Mr Brind, whose guidebook on Lewis is being republished, said: “I’m almost ashamed of how little Oxford does when it comes to C.S. Lewis. I have been fighting this battle for so long but nobody wants to do anything.

“At least there is now a plaque on the house but there are no signs showing the way to Lewis’s house. When it comes to the grounds the trust is more concerned with water voles than Lewis. So many trees have been cut down. I call it the destruction of Narnia.”

Andy Gunn, of the Berkshire, Buckinghamshire and Oxfordshire Wildlife Trust, has been involved with managing the nature reserve for the last two years.

During that time he says he has overseen a group of volunteers who have rebuilt the C.S. Lewis bench, constructed a boardwalk to improve access and created a pond-dipping platform for children to use.

He said: “The C.S. Lewis nature reserve is a very popular site for local people and schoolchildren to visit. Local schools visit once or twice a week for learning outside the classroom activities.

“The ponds on the reserve are noted for damselflies and dragonflies in the summer, and birds including heron, kingfishers and coots.

“This autumn there’s been a good display of fungi such as the collared earthstar and common puffball.

“When we restart the volunteer group next year, they will be carrying out practical conservation work that’s needed to maintain this special habitat for woodland wildlife.”

Ironically, the man behind the sheltered housing plan, Jonathan Beecher, met Lewis and has known Mr Gresham for many years.

Mr Beecher, who could scarcely be more different to the stereotype of the property developer, said his proposal could create units for a small community of elderly people who enjoy the arts.

“We are proposing high-quality architecture and people would be able to share these grounds with us. It would fit in nicely with the space we have.”

For him the nature park now looks desolate. “The nature reserve is a wonderful site,” he says. “But it is now quite worn-out looking and unloved.”

At least he agrees with his old friend Mr Gresham on one thing, as yet another battle for Narnia looms.