Into the woods: Radiohead's in-house artist captures Britain's hidden forest walks

'I was in the studio with Radiohead while they were recording King of Limbs and, as the music played, I got this impression of a cathedral of sound, this beautiful overarching music, and I felt it deserved to be played in a cathedral – not in a cathedral of religion, but a cathedral of nature," explains Stanley Donwood.

Donwood is an artist and the creator of Radiohead's album artwork since The Bends in 1995. "It got me thinking about how the ceiling tracery and fluted columns of churches owe their form to the interlocked branches and tree trunks of the forest. I decided I wanted to free that imagery from religion and give it back to nature."

He began to paint trees. Stridently colourful trees in oils and spray paints, with black mists dancing between them and creatures permeating through the darkness. And as he progressed, the idea began to branch in new directions and grow into something larger.

"Soon after I began working on a book with [the writers] Robert Macfarlane and Dan Richards, based on our experiences camping and walking in the holloways of Dorset," says Donwood.

"These holloways are hidden footpaths created by tunnels of interlocked branches. I had read about one in particular, which formed the basis of a description in Geoffrey Household's 1939 novel, Rogue Male, and the idea of this holloway fascinated me so much I wanted to experience what it was like to be within it."

The book became Holloway, which was later picked up by Faber and Faber for a wider release. Donwood created the illustrations. Gone were the colours and the ghosts of his Radiohead work, and instead Donwood produced very straight depictions of holloways in pencil and ink and in a limited palette of black and white (though it was limited partly through necessity, as the way it was printed – on a Heidelberg platen press – restricted the colour choice).

The idea had shifted. But Donwood's process remained the same.

"They are all experiential renderings of the forests I camped in and walked through, they are images that have gone through a filter of time and a filter of my own imagination," he explains.

Later, after Faber published Holloway, Dan Richards returned to Household's holloway to record 24 hours of audio in the tunnels. When he got there, he found it had gone.

"It had been completely taken apart, destroyed by machines," says Donwood. "It was a microcosm of what is happening globally. We are losing our natural habitats. When Dan discovered that the holloway had disappeared, I realised that through the artwork I was carving its gravestone."

These aren't pretty pictures of the forest. They aren't just pictures full stop. Now hung together in an exhibition at The Outsiders Gallery, the body of work is as much a physical experience as a visual one. It takes you into those tunnels of trees, into those natural cathedrals, and challenges you to make sense of it all.

"The whole idea is that we, as a species, spent so much time in the forests," says Donwood. This is his attempt to take us back there.

'Stanley Donwood: Far Away is Close at Hand in Images of Elsewhere' is at The Outsiders Gallery, London W1, to 19 October; slowlydownward.com