The Undercliff: Lyme Regis's Wild National Nature Reserve

Just east of Lyme Regis, the land itself has given way to create one of the most extraordinary walking landscapes in England — a five-mile corridor of collapsed cliffs, impenetrable scrub and dense woodland that has been largely left to its own devices for nearly two centuries.

Most of the Jurassic Coast can be understood at a glance: the cliff geology laid out in horizontal bands, the beach below, the sea beyond. The Undercliff resists this kind of reading. It is a landscape that disorients. The path twists and dips through tunnels of vegetation so dense that the sea, which must be close, becomes invisible. Old chalk masses tilt at improbable angles. Ash trees have colonised the rubble left by falls that happened a hundred and fifty years ago and grown tall enough to close out the sky. It is, by some distance, the most unusual nature reserve on the South West Coast Path, and one of the most ecologically rich stretches of coastal habitat in England.

The Axmouth to Lyme Regis Undercliff National Nature Reserve was designated in 1955 and covers roughly 790 acres of the collapsed cliff zone running from the edge of Lyme Regis westward to the mouth of the Axe at Seaton in Devon. The reserve exists because this ground has been largely left alone — no agriculture, no forestry management, no grazing. The result is a rare example of what ecologists call succession: the natural process by which bare ground or disturbed land is colonised by plants and then by the animals that depend on them, without human interference in the sequence.

The landslide of 1839

The Undercliff owes its character to a single catastrophic event. On the night of 25 December 1839, a section of cliff between Lyme Regis and Seaton collapsed dramatically when water percolating through the chalk above found the underlying greensand and gault clay and lubricated a vast mass of rock and soil. Approximately eight million tonnes of material slipped seaward, creating a chasm of up to a hundred feet deep and leaving a chaos of displaced ground, tilted fields and ruined cottages behind it. A corn crop that had been planted in the fields the previous autumn emerged the following summer from the rubble, and the event attracted enough public attention that excursion boats came from Weymouth to view the spectacle.

Since then, smaller slips have continued steadily. The underlying geology — impermeable clay beneath water-bearing limestone and chalk — creates conditions for ongoing movement, and the Undercliff path is periodically rerouted or temporarily closed when sections of the route become unsafe. This is not a relic landscape preserved under glass; it is still actively changing.

Wildlife in the tangle

The dense, undisturbed vegetation of the Undercliff supports a range of species that are scarce or absent in more managed coastal habitats. Roe deer move through the scrub, occasionally visible at dawn or dusk in the more open sections. The reserve is noted for its butterfly populations: White Admiral, Silver-washed Fritillary and Speckled Wood are all present, along with a range of common species. The humidity and warmth created by the sheltering cliffs above produce micro-habitats suited to rare plants, including several species of orchid that colonise the disturbed ground.

Birdlife includes breeding Chiffchaff and Blackcap in large numbers, both species taking advantage of the miles of dense scrub edge. Peregrine Falcons nest on the cliffs above the reserve. In winter, the dense ivy and bramble thickets hold Woodcock and Song Thrushes, and the occasional Firecrest winters in the more sheltered sections.

Practical walking tips for the Undercliff path

The path through the Undercliff is one of the more demanding sections of the South West Coast Path, but it is achievable for reasonably fit walkers who go prepared. The following tips will help:

1. Allow a full day. The five miles from Lyme Regis to Seaton take between three and five hours depending on pace and conditions. There are no shortcuts once you are inside the reserve.
2. Check the path status before setting off. Natural England and the South West Coast Path Association post notices when sections are closed due to fresh slippage. It is worth checking online the day before.
3. There is no exit mid-route. Once you leave the Lyme end, there is no way off the path until Seaton at the far end. Make sure everyone in your group is comfortable with the full distance.
4. Carry water and food. There are no cafes, shops or facilities of any kind within the reserve. Bring more water than you think you need, particularly in summer.
5. Wear proper footwear. The path is frequently muddy, steep and uneven. Trail shoes or walking boots are essential; trainers are inadequate.
6. Do not leave the path. The ground on either side is unstable and the vegetation is genuinely impenetrable in places. The path is narrow enough in sections; do not be tempted to explore off it.
7. Arrange return transport in advance. The Lyme Regis and Seaton ends are about nine miles apart by road. Either arrange a taxi or check bus times between the two towns before you start, so you are not stranded.
8. The Lyme end is the easier start. Beginning from Lyme Regis means the majority of the elevation gain comes early, which most walkers find more manageable than the alternative.

The Undercliff is not a walk for everyone, and it demands a commitment that the more accessible stretches of the Jurassic Coast do not. But for those who make it through, the sense of having traversed something genuinely remote and wild — within a mile of one of Dorset's most popular seaside towns — is considerable. The reserve represents a kind of accidental rewilding on a grand scale, and the experience of walking through it is unlike anything else the South West Coast Path has to offer.

It begins, as so many good things in this part of Dorset do, at the edge of Lyme Regis, just where the town gives way to the coast path heading east. The entrance to the reserve is modest — a gate, a notice board, a narrow track descending into the trees. Within a hundred yards, the town disappears entirely.