Oxford has long been a portal into other worlds.

Lewis Carroll's Alice was a real-life friend of the author, who joined him on trips up The Thames before disappearing into Wonderland through a mirror. And the heroes of Philip Pullman's His Dark Materials slipped into a parallel Oxford after finding a tear in the fabric of the universe in Summertown.

Frodo (Elijah Wood) in Middle Earth.

Wonderland is fantasy but Pullman's alternative Oxford is close to the real thing - and the imagined lands of J R R Tolkien and C S Lewis may also have some reality, in a little-known Oxford woodland.

It was once owned by Lewis, who dreamed up the land of Narnia as the setting for The Lion, The Witch and The Wardrobe and subsequent books.

Lewis and Tolkien - creator of Middle Earth and other lands in the Lord of the Rings trilogy - were friends. Both were academics and fellow members of the Inklings group of writers who met in the Eagle and Child pub in Oxford.

Lewis often rowed on the lake, and a partly-submerged boat that remained for many years was reputed to have belonged to the writer.

There was an atmosphere of mystery and a pervading feeling of oddness about the place

Douglas Gresham, stepson of C S Lewis

Now the woods off Lewis Close, east of the city, have been renamed the C S Lewis Nature Reserve.

They are maintained by BBOWT, the wildlife trust for Oxfordshire.

Gavin Hageman of BBOWT said: "It's long been thought that this reserve inspired Lord Of The Rings, and Middle Earth was something Tolkien dreamed up while walking in it.

"You see all the veteran trees and it brings it into your mind."

Huge stones in the woods are said to resemble gremlins.

For a long time the reserve was used for illegal fly-tipping. But then BBOWT tore down barbed wire to open it up to the public, and cleaned up damage by vandals.

The Lion, the Witch and the Wardrobe come to life in an Oxford wood.

"Our policy previously had been to fortify it with barbed wire because we had a lot of problems with kids riding mountain bikes and people fly-tipping," said Mr Hageman.

"But we had a change of policy and cleared away all the barbed wire and put in much more friendly access.

"It's particularly relevant at the moment because of the Lord Of The Rings films."

C S Lewis was fond of exploring the woods with his stepson, Douglas Gresham.

Mr Gresham later described its "half-ruined buildings and mysterious old sheds" in his introduction to The Complete Chronicles of Narnia, published in tribute to his late step-father.

He said it had something of the air of Narnia, the fantasy land children entered through the back of a wardrobe.

"There was an atmosphere of mystery and a pervading feeling of oddness about the place," he wrote.

"I was 10 when I went there to live and I was almost in Narnia."

If the woods were the inspiration for Narnia and Middle Earth, though, neither of their creators ever confirmed it.

And there are rival claims for the origins of Tolkien's imagined lands, including the Malvern Hills and the dark industrial corners of Tolkien's childhood home in Birmingham.