If you spend your weekends heading out into the fields and hills of England and Wales, you might not have come across the "Clems" yet. Unlike the big-hitting lists like the Munros or the Wainwrights, it’s actually one of the more niche, lesser-known classifications in the UK walking scene. For those who do know it, however, it’s a set of summits that offer that perfect mix of "significant but doable."

Edwin Darnley "Clem" Clements was born on March 15, 1923, in Farnborough, Kent. Though he eventually became a legend in the walking community, his professional life was actually spent looking at the stars. He wasn't a professional climber, he didn't have a YouTube channel, and he certainly wasn't trying to be famous. He was a guy who worked as a professional astronomer and spent every spare second he had outside, usually with a bicycle and a very sharp pencil.

So, who was the man who basically redefined how we classify our hills? And why should we care about a list he hand-wrote back in the early 90s?

The Day Job: Stars, Einstein, and Accuracy

To understand why the Clems list is so meticulously put together, you have to look at what Clem did for a paycheck. For 27 years, he was a professional astronomer at the Royal Greenwich Observatory.

Now, when we think of astronomers today, we think of people looking at high-res digital images from Hubble or James Webb. But back in Clem’s day, it was a lot more manual. He worked at Herstmonceux Castle in Sussex, and his specialty was "astrometry." Essentially, his job was to measure the exact positions of stars with incredible precision. He spent hours using machines to look at glass plates of the night sky, marking down coordinates that had to be perfect.

He was even part of the team that re-measured the famous 1919 solar eclipse plates. That was the study that proved Einstein’s theory of General Relativity was right by showing that gravity could actually bend light. Imagine that for a second: the guy who decided which hills in the Lake District count as "Clems" was the same guy helping prove Einstein right.

This professional background is everything. When Clem looked at a map, he didn't just see a "big hill." He saw data. He saw contours, heights, and distances that needed to be categorized with the same scientific rigour he applied to the stars.

The Original "Ultra-Walker"

Long before "ultramarathons" and "fastpacking" were trendy, Clem was out there doing the real work. After World War II, he became a "Munroist"—someone who climbs all the Scottish peaks over 3,000 feet. But he didn't do it the easy way.

Clem didn't drive. Ever. He never even learned how.

If he wanted to go to the Scottish Highlands from his home on the south coast of England, he’d hop on his bicycle and peddle. In 1949, he cycled all the way to Braemar just to start his walking tour. Think about the fitness that takes. He was known for being perpetually tanned because he spent so much time on his bike in all weathers.

He was also famous for taking his bike where most people wouldn't dream of. There are stories of him reaching the summits of places like Cross Fell or Glas Maol and just having his bicycle right there with him. He was the ultimate "open-air man." He just loved being out in it.

What Exactly Is a "Clem"?

So, let’s talk about the list. How did we get from an astronomer on a bike to a classification used by thousands of hikers?

In the early 90s, Clem decided that the existing ways of counting hills were a bit… well, messy. Some lists focused purely on how high a hill was above sea level. But Clem (and a fellow named Dr. Eric Yeaman, whose work Clem built upon) felt that height alone wasn't enough.

They were interested in "prominence."

The idea is simple: for a hill to feel like a real, independent mountain, it needs to stand out from its neighbors. If you’re standing on a summit and there’s a slightly lower bump 50 meters away, is that a "new" hill? Probably not.

In 1993, Clem sat down and produced a handwritten list of 1,284 summits in England, Wales, and the Isle of Man. He used what we now call the "Yeaman Criterion," but he applied it with his signature astronomer’s precision. To be a "Clem," a hill has to meet one of two rules:

The 100-meter Drop: The hill has to have a "re-ascent" of at least 100 meters on all sides. Basically, if you want to get to any higher ground, you have to go down at least 100 meters first.
The 5km Rule: If it doesn't have that 100-meter drop, it must be at least 5 kilometers away from any higher point.

It was a brilliant way of making sure the list included hills that actually felt like hills, rather than just random high points on a long ridge. After Clem passed away in 2012, the walking community officially named the list the "Clems" as a tribute to the man who did the legwork (and the math).

The "Local Pimple" and 3,000+ Ascents

One of the best things about Clem was that he didn't just care about the big, dramatic mountains. He loved the "small" stuff too.

After he retired to Guildford in the 80s, he developed an obsession with his "local pimple"—St Martha's Hill. It’s a lovely spot, but it’s not exactly Everest. That didn't matter to Clem. He walked up that hill nearly every single day.

He kept a log of it, of course. By the time his health started to slow him down in 2011, he had recorded 3,720 ascents of St Martha’s Hill. In 1997, he did some quick math and realized that between his hill walking and his cycling, he had covered about 0.1% of the distance from the Earth to the Sun.

That’s the kind of mind he had. Everything was a record, everything was a measurement, but it was all driven by a simple, pure love for being outside.

No Computers, No Problem

You might think that a guy so obsessed with data would have loved the internet and GPS. Actually, the opposite was true.

Clem never used a computer. He didn't like them. He once said his brain was "so orderly" that he didn't need one. Instead, he kept everything in a manual card-indexing system. If you wanted to talk to him about a specific grid reference or a height log, you didn't send an email—you wrote him a letter.

He was a master of what he called "old-fashioned pen-pallery." He would correspond with walkers all over the UK and Ireland, sharing notes, correcting heights, and helping people find obscure summits. He even helped standardize the "Hewitt" list (Hills in England, Wales, or Ireland over 2,000 feet), ensuring that walkers across the Irish Sea were using the same metrics.

Why Clem Matters Today

Clem died in 2012 at the age of 89. He left behind a legacy that isn't made of statues or buildings, but of paper and paths.

For those of us who love hill-walking, Clem represents the best of the hobby. He reminds us that you don't need the latest high-tech gear or a carbon-fiber mountain bike to have an adventure. You just need a bit of curiosity, a decent map, and the willingness to keep going, even when the weather turns.

The "Clems" aren't just a list of coordinates. They are a map of a man’s life. Every summit on that list was something he likely studied, cycled toward, or stood upon.

So, the next time you’re standing on a windy summit in Wales or checking a map in the Lake District, take a second to think of Clem. He might not be as well known as Mr Wainright or Sir Munro but he’s probably the reason you’re standing exactly where you are. He was the astronomer who brought the precision of the stars down to the mud and the heather, and we’re all the better for it.

View The Clems Database

Learn More About Prominence

The Astronomer on the Hill: Getting to Know "Clem" Clements