Chalk to the south, clay to the north. Sun to the south, rain to the north. Woods to the south, fields to the north. The ridge of the South Downs I was walking had become a frontier in the landscape, dividing the world into realms of weather, light and colour. Underfoot, the track – of fine chalk, pure enough to write with – was glossy with recent rain. Ahead of me, it ran brightly off over the hills, dipping from sight before looping back up again.

The downs are the only high ground in an otherwise flat and low landscape, and this means that – as in the desert or on an ocean – you can sometimes see what weather will reach you hours before it arrives. For much of that morning I led a charmed life: monsoon-squalls sliding by to east and west. Then, just after noon, a big storm caught me: yellow sun-flare, dulling to sepia. Rain drilling the earth, and the path a river, gathering the water into a torrent that rinsed the chalk white again. I sheltered in a copse of oak and high-trunked beeches, and ruefully considered the claim of the French historian Hippolyte Taine that ‘the first music of England’ is to be heard in ‘the fine patter of rain on the oak trees’. That morning, there was nothing musical to the rain. It was military: weather war.

It was the first of many soakings for the day. During each shower, the world bleared and wove. I tried to time my miles between squalls, moving from cover to cover. Despite the rain, I felt delighted to be out and walking. Ahead of me lay several days on foot, and the path insinuating eastwards – in the old and innocent sense of the verb, from the Latin ‘insinuare’, meaning ‘to bend in subtle windings, to curve’. I had left that morning from Winchester, with the aim of following the ridgeline of the South Downs east for a hundred miles until it made sea-fall near Eastbourne on the English Channel.

That first night on the downs I slept in the dubious shelter of a forestry plantation called War Down, tucked into my little bivouac tent while the rain slipped down the conifer needles. I have spent more comfortable nights under canvas. Yet by dawn the rain had stopped, the air was warm and so I started early. Wild clematis smoked up the hedgerows. Creepers – bryony, ivy, honeysuckle, bindweed – slinked out along tree branches and hung down over the path like the slipped coils of snakes.

Somewhere near Amberley, a barn owl lifted from a stand of phragmites. I stopped to watch it hunt over the water margin, slowly moving north up the line of the river, pulling a skein of shrills from the warblers in the reeds. It was a daytime ghost, its wings beating with a huge soundlessness. East of Beacon Hill, I reached a sustained ridge of chalk. Whitebeam trees marked the path to right and left, with their grey-green upper leaves and their sharp silver unders. Emerging from a dark and yew-rich wood, I reached an open down that stretched ahead for two miles. White flints were scattered across the fields, with tumbleweeds of sheep’s wool bowling between them.

At dusk that second day I followed a hollowed path that wound up the wooded scarp slope of the downs east of Storrington. The path’s depth spoke of continual foot-passage over centuries, and I liked its design: it moved in roundcornered zigzags, an uphill meander. There in the forest, night was further advanced. I turned a corner and a badger bustled out of a bank of dog’s mercury, stopped, stared at me, its eyes giving a quick green jewel-flash in the dark before it barrelled on downhill along its path, and I followed mine uphill, out of the woods and onto the summit plateau of the downs, to a place called Chanctonbury Ring – where I now wish I hadn’t spent the night.

The Ring is a circle of beech trees, planted on a hilltop that had been the site of Bronze Age and Iron Age fortifications, and a Roman temple. In 1760, a young aristocrat from the scarp-foot village of Wiston named Charles Goring decided to add his own layer of history to the Chanctonbury earthworks. He planted beech saplings in a well-spaced circle and, according to one story, then carried bottles of water up the slope to irrigate his saplings daily on that arid summit. According to the other story, he got his servants to do this job for him.

Either way, the saplings took root and flourished, and eventually grew into a cathedral grove. For two centuries, Chanctonbury was the best-known landmark of the South Downs, but in 1987 the Great Storm blew in and wrecked the Ring. It is now missing most of its main trees, and its interior has reverted to a sprouting scrub of ash and bramble. Nevertheless, up there that evening it still felt surprisingly remote. Brighton glittered away to the southeast, like something far-fetched on fire. The Weald to the north was almost lightless. The sky was a tarnishing silver. I rolled my sleeping mat out between two of the remaining beech trees just as dark fell, and soon fell to sleep.

I heard the first scream at around two o’clock in the morning. A high-pitched and human cry, protracted but falling away in its closing phase. It came from the opposite side of the tree ring to where I was sleeping. My thoughts were sleepmuddled: A child in distress? A rabbit being taken by a weasel or fox? No, impossible, for the sound was coming from treetop height. A bird, then – an owl, surely? Yet this was like no owl I had ever heard before: not the furry hoot of a tawny or the screech of a barn owl. I felt a rasp of fear, then dismissed it as ridiculous.

Then another cry joined the first, different in tone: slightly deeper and more grainy, rising at its end; the shriek of a blade laid hard to a lathe. Also more human than avian, also unrecognisable to me, also coming from treetop height. I lay there for two or three minutes, listening to the screams. Then I realised, with a prickling in my shoulders and fingers, that the voices had split and were now coming towards me: still at treetop height, but circling round the tree ring, one clockwise and one anti-clockwise, converging roughly where I was lying. I felt like standing up, shouting, flashing a torch; but instead I lay still. The cries met each other almost directly above me, 20 or 30 feet up in the dark. After 15 minutes they stopped and eventually, uneasily, I fell back to sleep.

It was only later that I researched the folklore of Chanctonbury Ring. I now know it to be one of the most haunted places of the owns. Sussex folklore, mostly from the late 19th and early 20th centuries, was rife with examples of it as a portal to the otherworld. Arthur Beckett, in his 1909 The Spirit of the Downs, had reported that ‘if on a moonless night you walk seven times round Chanctonbury Ring without stopping, the Devil will come out of the wood and hand you a basin of soup’ in payment for your soul, which sounds like a poor exchange.

I also discovered that many people who had slept out at Chanctonbury had been forced to abandon the hilltop due to eerie events. In the 1930s, Dr Philip Gosse recorded in his book Go to the Country that ‘even on bright summer days there is an uncanny sense of some unseen presence which seems to follow you about. If you enter the dark wood you are conscious of something behind you. When you stop, it stops; when you go on it follows.’ Closest to my experience was that of a group of bikers who had spent the night at the ring in 1966. Things were quiet until after midnight, when a crackling sound started, followed by the wailing voice of a woman that appeared to move around the circumference of the ring. The motorcyclists fled, and subsequently complained of physical ailments, headaches and lassitude in the limbs. Reading that, I felt first a shock of recognition and then mild pride that I’d tolerated what had put a gang of hairy bikers to flight.

I woke to a kingfisher dawn: orange cumulus in the east and blue streaks in the cirrus cover overhead. I walked around the ring looking for any explanation of the night’s screams. None. A white chalk path spooled away east-south-east over high downs, so I followed it along Bramber Bank, a sloping shoulder of turf that dips gracefully into the upper valley of the River Adur. For half a mile of the bank, the path was littered with thousands of striped snail shells over which I crunched. A field to the north was pink with bursts of mallow, thrust up from the turf like magicians’ sprays of false flowers.

The sun was already hot by the time I reached the medieval church of Botolphs, where my friend Rod Mengham – a South Downsman by birth and upbringing, and a poet, archaeologist and writer by practice – was waiting in the shade of the tower to walk a few miles with me. I was very happy to see him.

East of the River Adur, the downs run in three long plateaux, separated by stream and river valleys. On the high point of the first, Edburton Hill, are the earthworks of a motte-and-bailey castle, which in spring and early summer are a knee-high wildflower meadow: agrimony, wild mignonette, red clover, yellow rattle, marjoram, scabious, knapweed and the odd tall bolt of fireweed, through all of which wander string-like stems of bindweed. Rod and I stopped there and lounged among the flowers, in a dry westerly wind, talking about the downland poet Edward Thomas, the downland painter Eric Ravilious, and why I should never have slept in Chanctonbury Ring.

We stumped on eastwards on tired legs, crossing B-roads, car parks and the dry valley of Devil’s Dyke, a steep-sided combe carved out of the permafrosted chalk during recent ice ages. By afternoon, high on the longest of the downs ridges – the Plumpton Plain – I looked longingly up at the buzzards, wishing for wings myself so that I could loft over miles in minutes.

At a four-way crossroads we stopped to rest and drink water. I lay on the ground by a gate, chewing on a grass stalk, too tired to worry about the nettles that sprouted thickly around the gatepost. I was delighted to be prone. I felt as though I could sleep there for a century. The turf was my couch, my divan, my ottoman. Nothing, I vowed silently to myself, would induce me to move from this position for at least an hour.

‘You know the reason there are so many nettles where you’re lying?’ asked Rod.

‘Disturbed ground?’ I ventured.

‘Of a kind,’ Rod said. ‘It’s almost certainly because so many animals have used this gateway as their toilet. Nettles love fertile soil.’

I spat out the grass stalk, scrambled to my feet and we went on our way.

At Kingston, Rod left for London and I turned up Jugg’s Road, the broad old footpath from Brighton to Lewes that leads onto the summit plateau of Kingston Down. I dawdled over the plateau, looking for a place to sleep. I passed dewponds and tumuli, and a big field mushroom lying upside-down on its cap, its black gills like the charred pages of a book. Eventually, I decided on an area of lush turf, between two gorse bushes that would serve as windbreaks. The turf was rich with lady’s bedstraw, which seemed like a good plant to have as my mattress, though sweaty walker’s bedstraw would have been a truer name that night. Hundreds of feet above me, skylarks trilled on, the notes of their songs falling like ticker tape.

The skylarks sang me to sleep, and they woke me before dawn. I walked down into Lewes as the day was forming, and then onto the southern slopes of Mount Caburn, the only major summit of the downs that outlies the main chain. Purple heads of marjoram thrummed in the warming breeze. I picked up a scabious head and pinches of wild thyme. Near Glynde, I crossed the Ouse: the river mucky-banked, beginning to loop as it neared its floodplain and the sea. The path climbed again, up onto Firle Down, past teasels flowering purpley blue.

Late in the day, achy in the legs, I reached Cradle Hill, into whose eastern slope a great white chalk horse has been cut. Below me the River Cuckmere made its greasy meanders towards the sea. I dropped off the scarp down to the river, and then along the edge of the Cuckmere for two or three miles. The river water was the colour of milk chocolate. The brown mud of its banks was a rich text of bird prints, and my boot marks joined the tracks of heron, cormorant, gull and egret. An hour before dark I stood on the summit of a small chalk bluff, from which I looked down onto Cuckmere Haven, the point at which the river reaches the English Channel. It is a wide bay of flint shingle with a shallowly sloping foreshore, and was formerly guarded by slumping pillboxes. Coastguard cottages perch on the high ground to its west and, to its east, the white cliffs of the Seven Sisters are strung out like a line of washed and pegged sheets.

Little fledgling owls made test flights between the branches of sycamores. A pale horse stood motionless in a cropped field, gazing northwards. The tide was high, and for a hundred feet away from the shore, the water appeared to be the colour of green milk, the waves having sluiced chalk from the foreshore and cliffs, which stained the sea white.  

I walked down to the shore and along the tide line, which was cobbled with flint boulders. Beneath the first of the Sisters, my eye was caught by a clutch of grey flints that lay together like eggs right at the foot of the cliff. I picked them up, one by one, amazed. Each one had a drawing of a creature on it, made in chalk. The style was that of the Lascaux cave paintings: naïve but fluent in line. A deer, a gull, a hawk, a seal, a human figure. Somebody must have been sitting here that afternoon, using a piece of chalk from the cliffs to draw those figures onto the flints.

I placed the largest of the stones on a flat outcrop of chalk, and then arranged the others above them in decreasing size order. Hawk, on top of seal, on top of deer, on top of human: a simple cairn at the rivermouth, marking my sea fall and the end of my walk.

Robert Macfarlane is the award-winning author of Mountains of the Mind and The Wild Places. This story is based on his new book, The Old Ways: A Journey on Foot.

The article 'England’s ghostly South Downs Way' was published in partnership with Lonely Planet Magazine.