Grenade Shaft: an incredible Stump Cross secret

How are caves discovered? Sometimes it's a happy accident – and sometimes it's the result of years of tenacious teamwork.

The discovery of Stump Cross itself was the result of happenstance. Two lead miners from a nearby village were looking for a seam – but instead, they dug into the caverns that you can visit today.

But a lot of caving work is carried out with grit and determination. It could be that a chamber is known to exist but hard to access. Or it could be that a connecting passageway needs digging out.

Grenade Shaft is a 48-foot natural drop across the road from Stump Cross. At the bottom is a wonderland of crystal formations – but one which, sadly, can't be opened to the public without causing unavoidable damage.

It's one of the many secrets of Stump Cross that we explored in a previous article – those chambers and passageways that lie beyond the show cave. These are the domain of hardy cavers, not casual visitors.

The discovery of Grenade Shaft is a tale of high hopes, false starts, decades-long collaboration – and a British hand grenade.

The dig begins

Our story starts in 1947 with the Craven Pothole Club – a group of cavers still active today.

In that year, member Len Cook and his friend John Frankland visited Stump Cross Caverns to meet with then-owner George Gill.

Gill took them round the show caves – and then showed them something intriguing across the road.

There in the ground was a shakehole. This is a steep-sided depression in the ground. Could there be some treasures to uncover?

North Yorkshire is dotted with manmade shafts – relics of the age of lead mining. But Grenade Shaft – at this point just an unassuming shakehole – was naturally occurring.

Gill was a cheerleader for excavation. He encouraged Cook and Frankland to dig out the shakehole and see if it linked up with the caves. There was speculation that it might connect with "Heaven" – a passageway filled with gorgeous rock formations.

This survey began in 1948 when a merry band of CPC members got to work.

It was an attractive prospect to some because it was above ground. Even the hardiest of cavers can sometimes get a little tired of the damp and dark of the caves.

The dig continued in fits and starts until 1954, by which point the team had dug 18 feet down.

Member Jack Bradley had a bright idea. When working as a dentist in Hong Kong, he had picked up an army souvenir – a live "Mills Bomb" hand grenade.

In the Stump Cross movie, this is where there'd be a swell of dramatic music and a slo-mo action sequence as Jack dropped the grenade into the shaft.

Sadly, it didn't do much. The hole was filled in and the project was abandoned.

Take two

Fast forward to 1964 and a party of diggers from the Yorkshire Underground Research Team (YURT) fancied a change.

They'd been hard at work on an underground dig and thought it might be more enjoyable to have a go at the shaft.

As they dug, they found Jack Bradley's grenade – instantly providing the shaft with a name.

At 48½ feet down, they came across a low chamber filled with stalagmites, glassy flowstone and a crystalline pool. Initial descriptions of "The Keep", as it was known, emphasise its glittering, sparkling surfaces and glorious formations.

The caving spirit

The discovery of The Keep is a great example of the teamwork and tenacity that cavers often have. Digs were often begun, abandoned and then picked up by another group. Over the decades, real progress is made.

The discovery of Grenade Shaft is exemplary in another respect. Cavers want to share the beauty of their discoveries – but they also want to protect them.

A famous example of this relates to Lascaux in southwestern France – home to some of the oldest cave paintings in the world.

As soon as Lascaux was opened to the public, the paintings began to deteriorate. After 15 years, it was decided with a heavy heart that the caves should be shut in order to protect them.

It's not dissimilar from the decision to cover Grenade Shaft. It's not just that you don't want non-specialists popping down for a look and causing damage – it's that the shaft is impossible to explore without doing so.

As well as striking straws and curtains, the shaft is home to extensive crystal floors. It's simply not possible for people to visit without causing damage to this glittering surface.

Situations like these put cavers and cave owners in a bind. On the one hand, you want to show off these natural beauties – not least because of all the hard work that went into their discovery.

On the other hand, you're a caver partly because you love these formations. Causing them damage would be unthinkable.

This second consideration usually trumps the first – and in the case of Grenade Shaft, it was a no-brainer.

It's a big change in mindset from that of the 19th-century lead miners who discovered Stump Cross. Back then, stalagmites and stalactites were seen as ornamental junk. Miners would clear them out and sell them to local hotels and restaurants.

From a visitor's point of view, it's a shame that the shaft can't be part of the tour – another chamber to match the glimmering expanses of the show cave.

And from a caving perspective, it's a shame that more digging work can't be done.

However, a 3D scan of the shaft has been made so that it can be visited without causing damage to the formations.

This was done in 2022. It required a large camera, a bunch of floodlights and an iPad. The team took photographs at three-metre intervals until they got a complete 3D picture.

Is there more to discover?

The story of Grenade Shaft tells us a lot about the tenacity of cavers as well as the balance that needs to be struck between discovery and preservation. And there are plenty more stories to tell. Keep your eyes peeled…

While you can't visit Grenade Shaft, there are countless wonders to discover within our show caves. Fancy an awe-inspiring day out in Yorkshire? Book today and prepare for an adventure you won't forget.