The South West Coastal Path stretches for 630 miles. And the most walked mile of the entire trail is between Lulworth Cove and Durdle Door, the ancient stone arch which is arguably the British coastline’s greatest natural feature.

“We have around 750,000 visitors a year,” says Derek Billings, education ranger for the Lulworth Estate. “We have 6,000 students and schoolchildren; we even had Len Goodman recently!”

Nearly half their visitors will do just one thing: walk from the estate’s car park at Lulworth Cove to Durdle Door. “That’s all they want to do,” says Derek.

And who could blame them? The Door has become an international icon, appearing on anything from outdoor sports advertisements, to advertising – without the estate’s prior knowledge! - a Middle Eastern Kingdom. Derek has swum through it several times; “It’s only about three metres wide from below.”

But there is so much more to Lulworth than its beautiful limestone arch.

There is the Lulworth Crumple, the geologically stunning rocks – and Derek’s favourite part of the whole estate – at Stair Hole. There are Man O’War Bay and Bat’s Head - which looks nothing like a bat, by the way.

There is the Fossil Forest and the scheduled ancient monuments lurking under the chalk grassland on the cliff-tops. There is the tiny Lulworth Skipper butterfly (discovered on this coast in 1832), the Dartford Warbler, the Portland Spurge and the Viper’s Bugloss. There are lizards, seagulls, dolphins and the occasional stray puffin.

“We are home to 35 of the 59 species of British butterfly,” says, Derek, proudly, as a Marble White flutters by.

“We had one man who travelled down from Manchester with the specific intention of seeing a Lulworth Skipper. It was the last UK butterfly on his list and now he’s seen them all.”

On top of all this, there is the plethora of public bodies they have to deal with as they go about their work.

Their stretch of coastline is part of the Jurassic Coast UNESCO World Heritage Site, it’s a Site of Special Scientific Interest and an Area of Outstanding Natural Beauty.

The village of Lulworth is a Conservation Area and they also have to work with the Ministry of Defence, which leases land to use as Army ranges, as well as the requirements of Natural England. The rangers have to keep an eye on more than 20 scheduled Ancient Monuments, plus two Higher Level Stewardship management areas.

And then there are the activities they host; from coasteering, guided walks, photographic courses, stone-carving days and Rockpool School, where Derek takes tots to learn what lies beneath the stones and seaweed on the shore, and why we shouldn’t put 20 crabs in a bucket together. “They fight!”

On the day I arrive they are preparing for an outdoor play performance and the looming Camp Bestival for which Ranger Tom Oliver has been checking trees and the team have been giving the odd hedge and gate entrance a light strimming.

But all this falls on top of their daily work, which includes looking after everything on their 12,000 acres of land; from broken fences to keeping numpty tourists off Durdle Door itself, in case they plunge off the thing to their deaths.

“Because of the cliff danger we ask people not to sit at the base of them as even a tiny stone falling from the top could seriously harm you,” says Derek.

“One tourist told us it didn’t matter because ‘if it was dangerous there’d be signs all along’ which is daft when you consider that a few years back such a huge pile came down that the coastal path had to be re-routed.”

They remember the day they liberated a host of Adonis Blue butterflies, after they suspected a man of illegally collecting them.

“One of the most satisfying things we’ve ever done,” says Derek.

And they also have to manage the expectations of irate walkers who are dismayed to find that parts of the path are closed when the Lulworth Army Ranges are firing.

They have to deal with all manner of accidents, including the day a father was struck in the eye when the stone his son chucked innocently into the sea bounced back and hit him.

And they have to physically care for this landscape which encompasses just the185 million years of history.

“We have five different rock types and fossils up to 125 million years old,” says Derek, picking up a stone to show me some fossilised worms.

They have a comprehensive programme for schools and education establishments and also for the visitors who want to know more about the area.

Derek wants to introduce a residential curriculum-based series of activities so that students can see up close, the geography or geology or fauna they are learning about.

There are enough fantastic facts and amazing statistics about Lulworth to fill a book. But perhaps the most amazing fact of all is how all this is funded. Give or take the odd grant, and fees from commercial users, the main bulk of money comes from... the car park.

“From the free butterfly walks to the loos, it pays for everything,” says Derek.