Suffering post-holiday blues, I needed a walk that would transport me into a different world, starting from my own doorstep.

So I decided to enter the world of Narnia — not through a wardrobe, like the children in C S Lewis’s books, but by walking up Headington Hill, where the author, an English don, became a born-again Christian in 1929.

“The odd thing was that before God closed in on me, I was in fact offered what now appears to be a moment of wholly free choice. I was going up Headington Hill on the top of a bus. Without words, and almost without images, a fact about myself was somehow presented to me. I became aware that I was holding something at bay. I felt myself being given a free choice. I could open the door or keep it shut. I chose to open.”

One of the most surprising things was that he was on a bus at all. He was travelling from Magdalen College to visit his friend Mrs Moore, who lived in Holyoake Road, Headington.

He was a keen walker, and that was his only recorded bus journey. Later in life he walked to Magdalen each day from his home in Risinghurst, via the Fellows’ Garden, now padlocked but once a popular and beautiful route to Oxford city centre.

In the vacations he covered hundreds of miles in the Chilterns and the Welsh borders with his brother Warnie, following a long tradition of rambling academics.

The wonderfully wide raised footpath on Headington Hill was the brainchild of 18th-century don Josiah Pullen, who also walked almost every day from Magdalen to his home at the top of the hill, and raised money from the university to level out the rough hollow-way leading from Oxford to what was then countryside.

Before 1775, the London road had followed Cheney Lane, where a 1667 milestone reads “Here endeth Oxford mile hy way”, showing that the City Fathers were no longer responsible for its upkeep. Eagle-eyed history enthusiasts can spot other highway stones on the newer road.

I climbed up to admire the beautifully decorated cast-iron bridge, pausing to remark on the Narnia-style lamppost, similar to the one in my Puffin edition of C S Lewis’s The Lion The Witch and The Wardrobe, which first led me into Narnia.

Anyone can use the bridge to walk to Headington Hill Hall — a magical place, and a fine pleasure for anyone who remembers its former owner, the disgraced tycoon Robert Maxwell, who — having promised to increase public access — turned the site into a fortress, with barbed wire and video cameras fixed to trees. The grand mansion, now the scene for Oxford Brookes University graduations and civil wedding ceremonies, was built for the Morrell family, whose fortune came from brewing beer.

It was bought by Oxford City Council in 1953, with 20 acres becoming a park and the house being let to Maxwell for his publishing business Pergamon Press, whose employees’ pension fund he plundered.

The view from here is grand, though screened by Headington Hill Park’s magnificent collection of trees. From Nuneham, Bagley and Wytham woods, it stretches to include glimpses of the towers of Oxford’s other university.

I left the Brookes grounds through the gate to Cuckoo Lane, an ancient track to Old Headington which is attractively rural at this point before crossing Headley Way and becoming incorporated into Woodlands Road. The ‘Cuckoo Lane’ end of Oxford United’s Manor Ground was once notorious as away fans had to be escorted by police during the football hooligans’ heyday of the 1980s.

At the end of the Manor, now a private hospital, Cuckoo Lane narrows into a spooky dark tunnel, created by William Wootten-Wootten, owner of Headington House, who built two bridges across the right of way to link his land, leaving passers-by to duck through a subterranean passage.

I emerged on to Old High Street, pausing to look at the plaque on the home of C S Lewis’s wife Joy Davidman, whom he married at what is now the Nuffield Orthopaedic Centre after she was diagnosed with cancer. Their relationship was dramatised in the film Shadowlands.

It was coffee time, and the Davidman house is bang opposite Jacobs and Field, so another pause was called for before an exploration of Bury Knowle Park, another of Oxford’s public parks that was once the grounds of grand mansion.

Admiring the Narnia-inspired playground and Story Book Tree, based on stories by Lewis and Tolkien, and avoiding the ha-ha, I crossed the London Road to head along Ramsay Road towards Headington Quarry, joining the route of the old funeral path, famous for the riots of 1807.

It was the owner of Bury Knowle house, Joseph Lock, who brought the Quarry coffin bearers to court for smashing down the wall he built across the traditional route to Old Headington church.

The first section of the route survives in Chapel Alley, but as a result of the dispute Quarry residents set up their own Methodist chapel and abandoned the Church of England. Eventually they were given their own church as well — Holy Trinity, designed by George Gilbert Scott, also responsible for the Martyrs’ Memorial and Exeter College Chapel.

C S Lewis, known as Jack, is buried here, along with his brother Warnie, who shared his house at The Kilns, which would have been a pleasant walk from the church when they lived there in the 1930s.

The church has a Narnia window, a memorial to a brother and sister who died at two and 16. The faces in the window were modelled from children who were in the congregation when the window was designed in 1991.

We followed a footpath signed to Shotover next to the Masons Arms, opposite the church, but decided not to take the final section, which means braving the Oxford bypass without a controlled crossing. Instead we used the traffic lights and walked up Kiln Lane to the Kilns.

Lewis’s first children’s book, The Lion, The Witch and The Wardrobe, was inspired by his experience of hosting evacuees here during the Second World War and the main character, Lucy, is named after one of them, who became his goddaughter.

Narnia had many inspirations, but surely must have been influenced by his surroundings. He and his brother had bought a house in the country, approached by a muddy lane — “Jack and I went out and saw the place, and I instantly caught the infection. The view from the cliff over the dim blue distance is simply glorious,” said his brother.

Now, with the Oxford bypass and the houses of Risinghurst, The Kilns seems part of suburbia. But the traffic noise disappeared as soon as we entered the C S Lewis nature reserve, once part of his garden. It is a damp spot, shadowed by huge trees, with Victorian claypit ponds fed by springs, formed by rain seeping through the sandy top of Shotover on to the Oxford clay.

In The Lion, The Witch and the Wardrobe, the witch has cast a spell so that it is always winter, but never Christmas. No one who has read it can forget the melting snow, signifying the arrival of the lion Aslan, and the arrival of spring, with celandines and snowdrops, buds forming and a dawn chorus of thrushes and blackbirds.

In the CS Lewis nature reserve, toads migrate to spawn, followed by dragonflies and damselflies in summer. Large moss-covered boulders known as ‘sandstone doggers’ look as if C S Lewis’s Narnian giants could use them as cannonballs.

The ponds are lovely, but no one would think of swimming here, as C S Lewis apparently did. He said in a letter: “The Kilns has been delightful. I know the pond looks dirty, but one comes out perfectly clean. I wish you could join me as I board the punt in the before-breakfast solitude...”

Walking up the steep slope (made easier by wooden steps, but still slippery), you can exit the nature reserve to rejoin the footpath from Quarry to Shotover. “The view from the cliff” is now obscured by trees, but the “dim blue distance” of Otmoor can be seen as you emerge.

The cliff is interesting, because it plays a central role in The Silver Chair, where the children arrive in Narnia by falling down a precipice that “goes on below the top of the very highest cliff you know, ten times as far, twenty times as far”.

Lewis, who apparently had a fear of heights, walked here a great deal, according to his friends. Shotover, fortunately, is firmly in public ownership and he was one of a long line of Oxford dons who loved the place.

Despite the car park, it is easy here to escape suburbia — we are in the ‘eastern wild’, which must have sown the seeds for the world of Narnia.

We intended to follow the green signs, but — as in any good children’s adventure — we got lost, then found our way home, using the ‘deep magic’ of the woods.

* The Oxfordshire.gov.uk website has a Shotover circular walk including the C S Lewis nature reserve, and Stephanie Jenkins’s website headington.org.uk has information about Lewis’s Headington life and a Cuckoo Lane walk. The Stagecoach number 9 bus stops every half hour at Kiln Lane, opposite Lewis Close, the entrance to the CS Lewis nature reserve, www.stagecoach.co.uk

* See my website groundhogwalking.co.uk