The way we look at the landscape of England, Wales, and the Isle of Man changed significantly toward the end of the 20th century. For a long time, the focus for anyone heading into the hills was almost entirely on absolute altitude—the height of a summit above sea level. This was the era of the "imperial" lists, where reaching 2,000ft (609.6m) or 3,000ft (914.4m) was the primary goal. However, in the late 1980s and early 1990s, a new perspective began to take hold. It wasn’t just about how high a hill was, but how much it stood out from its neighbors. This is the concept of topographic prominence, and the Clems list is one of the most significant historical markers of this shift.

The Clems exist because of a desire for objective, mathematical standards. Before this, lists like the Munros in Scotland relied on a mix of height and a subjective sense of "sufficient separation." The Clems replaced that vagueness with two hard rules: a vertical drop or a horizontal distance. It moved the conversation from "Does this feel like a separate mountain?" to "Does the map prove this is a separate mountain?"

Essential Statistics of the Clems

Feature	Detail
Total Count	1,298 summits
Height Requirement	None (Defined by Topography)
Prominence/Drop Rule	100m (328ft) OR 5km (3.1 miles) walking distance
Highest Point	Whernside (736m / 2,415ft)
Lowest Point	Scout Hill (285m / 935ft)
Most Remote	Isle of Man summits (28 peaks meeting the 5km rule)
Easiest Access	Benson Knott (319m / 1,047ft)
Hardest to Summit	Wild Boar Fell (708m / 2,323ft) or Margery Hill (546m / 1,791ft)
Authority/Keeper	The Legacy Committee

The Genesis of the List

The classification is named after E. D. "Clem" Clements. He wasn't just a casual walker; he was a systematic researcher with a background in meticulous field recording. Between 1960 and 1990, Clements worked as the chief recorder for the Mammal Society, specifically focusing on badger setts. He surveyed roughly 10,000 square kilometers (3,861 square miles) of southeast England, mostly by bicycle, and mapped over 1,000 main setts.

This background in biological surveying—where you have to be incredibly precise about georeferencing and categorization—was the perfect training for hill listing. In 1993, Clements took the "Yeaman's criteria" (pioneered by Dr. Eric Yeaman in Scotland) and applied them to England and Wales. His original handwritten manuscript listed 1,284 summits. This document was initially referred to as the "Yeamans of England and Wales," reflecting its methodological debt to the work done north of the border. At first, people called them the "Yeomans," but after Clements died in 2012, the community formally renamed the list "The Clems" to preserve his legacy and recognize his massive contribution to the field.

The transition of this list from a handwritten notebook to a digital database was a major collaborative effort. People like Rob Woodall, Myrddyn Phillips, Gary Honey, and Bernie Hughes worked to sync Clements' original observations with modern grid references. It wasn’t just about copying data; it was about honoring the thousands of miles Clements covered on his bike and on foot. It was a project rooted in respect for the systematic recorder's bias—the drive to catalog the natural world in its entirety.

The Logic of Prominence and Isolation

The Clems operate on a "dual-track" system. To be on the list, a hill has to meet one of two specific criteria. This distinguishes them from more modern, purely prominence-based lists like the Marilyns or the HuMPs.

The first is the Prominence Rule. A hill needs an ascent (or "drop") of at least 100m (328ft) on all sides. This means if you are on the summit, you have to descend at least 100m (328ft) before you can start climbing toward a higher point. This 100m (328ft) threshold was a significant departure from previous imperial lists, such as the Corbetts in Scotland, which required a 500ft (152.4m) drop, or the Hewitts, which utilize a 30m (98ft) prominence threshold alongside a 2,000ft (609.6m) height requirement.

Learn More About Prominence

The second is the Isolation Rule, which is a hallmark of the Yeaman influence. If a hill doesn't have a 100m (328ft) drop, it can still qualify if it is at least 5km (3.1 miles) in "walking distance" from any higher point on neighboring hills. This isn't "as the crow flies"; it’s the distance a human actually has to travel on the ground. This rule acknowledges that a hill can be significant simply because it stands alone in a wide area, even if the surrounding terrain is relatively flat. The use of walking distance introduces a human-centric dimension to the classification, suggesting that the significance of a hill is determined not just by its height, but by the physical effort required to travel between it and its higher neighbors.

Accuracy and Modern Surveying "Wars"

When Clements compiled his list in 1993, he was using paper Ordnance Survey maps with 5m (16.4ft) or 50ft (15.2m) contours. He had to interpolate heights and col depths by eye, identifying the highest point and the lowest connecting col. Today, we use GNSS (satellite) and LIDAR (laser scanning from aircraft) which can measure a hill to within a few centimeters.

This precision has caused high-profile reclassifications and technical "wars" in other classifications. For instance, the prominence of Moel Siabod was revised from 600m (1,968.5ft) to 599.7m (1,967.5ft) based on modern data, which caused it to be removed from certain "Majors" lists. For the Clems, these technological advances serve to verify why Clements chose certain hills in the first place. However, the list is maintained as a "static historical record." The Legacy Committee decided that even if modern LIDAR shows a hill is slightly short of the 100m (328ft) drop, if it was in Clements' original manuscript based on the maps of the time, it stays. This provides a stable target that is rooted in the history of the sport rather than the latest satellite reading.

Comparison with Other Classifications

The Clems sit in a complex hierarchy of British hill classifications. Their relationship to other lists is defined by varying thresholds of height and prominence. They are more inclusive than the HuMPs (which use a strict 100m/328ft prominence rule but ignore isolation) because the Clems capture those 5km (3.1 miles) isolated peaks. However, they are far more restrictive than the Hewitts or Nuttalls. While those lists have over a thousand summits based on a 2,000ft (609.6m) height, the Clems focus on topographic character.

The "feel" of a Clem is different. While lists like the Munros or Wainwrights are often crowded, the Clems frequently lead walkers to more obscure and isolated parts of the countryside. You can have a very high peak that isn't a Clem because it's too close to a higher neighbor, and you can have a very low hill, like Scout Hill at 285m (935ft), that is a Clem because it is isolated. This encourages a broader exploration of the landscape, highlighting summits that are prominent features of rural areas not typically associated with high-altitude mountaineering.

Landscape and Linguistic Roots

The names of these hills often tell the story of the ground itself, using linguistic data from Gaelic, Welsh, and Cumbrian origins to describe the physical terrain. While the research focuses on the English and Welsh fells, the terminology used—like "Fell," "Knott," and "Dales"—comes from a mix of Old Norse and Cumbrian influences.

Fells: (from the Old Norse fjall) refers to the high, rugged mountains of Northern England, like Wild Boar Fell (708m / 2,323ft).
Knotts: Like Benson Knott (319m / 1,047ft), these are usually rocky outcrops or rounded hills that stand out from the main ridge.
Dales: The valleys that define the separation between the summits, as seen in the Yorkshire Dales where Whernside (736m / 2,415ft) and Ingleborough (724m / 2,375ft) dominate.

The list captures the "grit" of the landscape. In the Isle of Man, the 5km (3.1 miles) rule is particularly relevant. Clements identified 28 summits on the island that met the criteria. Many of these fail the 100m (328ft) prominence threshold but qualify as Clems because they are the highest points within a 5km (3.1 miles) walking radius, emphasizing their status as independent landforms on the island.

Extremes and Technical Challenges

The terrain of the Clems varies wildly, and some summits present significant technical challenges. In the Lake District and the rugged fells of the North Pennines, you can encounter technical ground, steep scree, and complex navigation. Wild Boar Fell (708m / 2,323ft) and Great Shunner Fell (716m / 2,349ft) are substantial mountains that require proper equipment.

The most difficult or technical peaks often involve navigating complex ridges where the "key col" is hard to identify without precise mapping. The Howgill Fells, home to The Calf (676m / 2,218ft), offer rolling but deceptively steep terrain. Even lower-elevation summits like Margery Hill (546m / 1,791ft) in the Peak District can be challenging due to the peat bogs and remote nature of the moorland.

There is also a psychological layer to the 5km (3.1 miles) rule. Unlike a straight-line distance, walking distance depends on the terrain and the route taken. This requires the walker to engage more deeply with the geography, mirroring the type of field research Clements conducted on his bicycle while mapping badger setts. It turns a simple walk into an exercise in topographic analysis.

Access and Sensitivity Walking

In terms of access, the hills in England and Wales are largely covered by the Countryside and Rights of Way (CROW) Act, which granted a right of "open access" to mountains, moorland, and fells. This is distinct from the Scottish Land Reform, which offers a broader "right to roam."

However, "sensitivity walking" is a core tenet of the community. This means respecting the environment—the same environment Clements spent his life recording as a naturalist. Whether you are looking at a badger sett on the Isle of Wight or a summit cairn in Cumbria, the ethic is the same: leave no trace and respect the landowners and the ecology of the fells. Clements' research on the Isle of Wight recorded 95 active main badger setts and established a relationship between location and woodland habitats; his work reminds us that these hills are active ecosystems, not just points on a list.

In the end, the Clems are a lot more than just a list of coordinates or a set of rigid mathematical rules. They are a snapshot of a particular era in the 1990s when our relationship with the landscape was shifting from old-school height-watching to a more modern understanding of topographic independence. E. D. Clements didn’t just sit at a desk; he got out there on his bike and on foot, applying the same professional focus he used for the Mammal Society to the very shape of the land itself. Whether you’re standing on the 736m (2,415ft) summit of Whernside or looking out from a low, isolated spot like Scout Hill at 285m (935ft), you’re participating in a legacy of systematic discovery. It’s about the grit of the walk and the satisfaction of finding those quieter, independent corners of the British Isles that often get overlooked. "Clem" left us a way to see the hills as they really are—distinct, separate, and full of character.

View the Clems Database.

Essential Resources

For those looking to engage with the landscape or understand the legacy of systematic recording in the British Isles, these resources provide essential context:

Natural England: The statutory body responsible for managing land and providing the official "Open Access" maps for hills and moorland within England.
Natural Resources Wales: The statutory body responsible for environmental management and maintaining the "Open Access" maps for the Welsh fells and mountains.

Hills Featured in the Research

Below is a list of the specific summits mentioned in the historical data, providing a snapshot of the geographic and topographic spread of the Clems.

Hill Name	Metric Height	Imperial Height	Region
Whernside	736.0m	2,414.7ft	Yorkshire Dales
Ingleborough	724.0m	2,375.3ft	Yorkshire Dales
Great Shunner Fell	716.0m	2,349.1ft	Yorkshire Dales
Wild Boar Fell	708.0m	2,322.8ft	North Pennines
The Calf	676.0m	2,217.8ft	Howgill Fells
Margery Hill	546.0m	1,791.3ft	Peak District
Kisdon Hill	498.6m	1,635.8ft	Yorkshire Dales
Benson Knott	319.0m	1,046.6ft	Cumbria
Scout Hill	285.0m	935.0ft	Cumbria
Moel Siabod	599.7m	1,967.5ft	Wales (Prominence example)

THE CLEMS: FINDING THE QUIET CORNERS OF THE COUNTRYSIDE