What lies beneath... the woman who knows the secrets of the Dales underworld

Her first taste of pot-holing came as a teenager and having met her partner of 30 years on one of her very first trips to the Yorkshire Dales, below ground has always held a special allure.

"I nipped through a particularly tricky cave without a second thought," says Marion. "I think he thought I was some incredible athlete, but in truth it was simply the fearlessness of youth."

What started out as a hobby, soon became a labour of love. Originally from Warrington, Marion studied for masters in geology at Sheffield University and now living a few miles from Settle, the caves beneath the Yorkshire Dales have, she admits, become something of an obsession.

"They are endless fascinating," says Marion, whose enthusiasm for stalagmites and stalactites is boundless. "The more I've learnt about the science behind these structures, the more my love has grown and every time I go underground, even to places I've visited hundreds of times before, I see something new."

After her studies, Marion embarked on a successful career in the nuclear industry, but the caves were never far from her thoughts and when she saw an opportunity with Natural England to put her years of knowledge to practical use, she grabbed it with both hands.

"The endless commuting and long hours had taken its toll and I was looking for something much closer to home," she says.

Now working with the conservation organisation, Marion has been charged with carrying out an audit of all the caves in the Yorkshire Dales. It's a big job. The area boasts 543 individual sites, many of them in designated sites of special scientific interest.

"When you ask people to describe the Yorkshire Dales, they'll talk about the rolling hills and the dry stone walls. They may well mention the peaks like Ingleborough and Penyghent or the market towns like Hawes, but few people know about the gems which lie underground.

"We are so lucky in this part of the world to have a huge network of natural caverns where ancient rivers and streams flow and where the stalagmites and sand banks hold vital information from how the landscape came to be the way it is and which hold key data about past climate change.

"Natural England had an agreement with Defra to ensure that by this year 95 per cent of these sites are in what's called a favourable condition. The amount of information can't be collected overnight, but we began 18 months ago and with help from the local caving community we are now about 80 per cent of the way there."

While many of the caves can only be accessed by expert pot-holers, there are others just a few yards from the road which many day trippers drive past without giving a second glance.

"This is a typical Victorian show cave," says Marion, striding up to the chamber entrance of Yordas Cave in Kingsdale. A couple of days before, she had been lugging wood to the top of the gill to mend the fence which surrounds the small abseil opening and her fellow cavers have also been busy removing candle stubs from the cave walls.

"In the past, caves like this were used for all sorts of events," she says, ankle deep in water. "They were often used for raves – the acoustics are pretty good and there was never any danger of upsetting the neighbours. People tended to see them as an open space where they could do whatever they wanted, but damage has been done."

The candles left a layer of black soot on the cave walls and the sand banks, which Marion has particular affection for, were unceremoniously trodden on. Fortunately, most of the caves have weathered the years well, but while the vast majority meet Natural England's favourable condition criteria, the work on ensuring their long-term protection has only just begun.

"Mud, sands and gravel may not be particularly pretty, but they are incredibly important," says Marion who is often found taping off the mud banks to discourage cavers from walking on top of them. "It's not about telling people you can't do that, but it is about making people aware of what it is they are standing on.

"The sediment is made up of remnants of historic landscapes and by taking samples from it, you can get a pretty accurate picture of how the environment has changed over the years. Gradually it will get washed away by flood waters, but until that happens we really ought to look after it.

"The vast majority of cavers want to do the right thing by the

environment, they have an emotional attachment to these places and are keen to do all they can to conserve them.

"When cave exploration began in the late 19th century, the techniques were obviously fairly basic. There was a big explosion in the 1940s and '50s and unfortunately that was when most of the damage was done. However, it is possible to repair broken stalactites and one of the aims of this audit was to give us a very detailed picture of which sites need the most attention."

While Marion is leading the Natural England project, she says she

couldn't have completed the work without the help of other cavers who have voluntarily filled out online assessment forms and passed on their own local knowledge of how the area has changed over the years.

"The Yorkshire Dales is blessed with people who for decades have been quietly doing their little bit to protect the place," says Marion. "There's a retired greengrocer who has been monitoring bat populations in the area for the past 50 years. No one asked him to do it, it's just something he's always been interested in.

"You can't buy that kind of knowledge and as part of the cave audit we have been able to buy him some monitoring equipment to help him take more accurate readings. Making use of what's already on your doorstep is really important and my job would have been a whole lot harder, if not impossible without that kind of support."

As well as her work for Natural England, Marion is also studying part-time for a Phd at Leeds University. Unsurprisingly, her doctorate is focused on the geology of the Yorkshire Dales and you get the feeling that when it comes to delving underground, Marion's work will never be done.

"The possibilities really are limitless," she says. "Caves hold so much information about how the landscape was shaped and the influence of changing climates.

"For me, they are also incredibly peaceful places. When you're pot-holing you have to concentrate wholly on what you're doing. You can't think about the housework that needs doing or any niggling things that have been troubling you at work.

"It's just you and the rock."