The Guardian | 20 December 1996

Hot pursuits: Potholing
The fourth dimension

Laura Ivill digs deep into her reserves of courage and dares to go underground

Most of us would rather spend the night in a broken lift with Bernard Manning. Caving has a terrible reputation, so bad, in fact, that I dared not tell any of my close relatives what I was doing.

Our guide for the day, Kevin Walker, has a theory about the PR problem. He says that the trouble with caving and potholing is that their enthusiasts disappear off the face of the earth while they are doing it and the only time the public get to hear – or see – anything is when a rescue takes place. And so many people have this irrational attitude to what they imagine will be some kind of claustrophobic nightmare – the same people who cram into a rush-hour tube every day. Yet thousands of men and women go vaving safely every weekend. At least, that is what I remind myself.

The forecast is fine and water levels low in the pupular Porth y Ogof system near Brecon, which is just as well because the river that flows through this system is know as the Mellte – Welsh for lightning – a reference to how fast the water can rise on occasions. Kevin had stressed the need to wear plenty of layers in order to keep warm. Later I am very glad of my rubber knee pads over rubber trousers, bizarre though they looked in the car park.

Kevin is actually the person responsible for cave resue in this system, but no one can make you feel totally safe. I was unsure how I would feel squeezing between cracks in the dark under tons of rock, but I wanted to find out because I had this romantic vision of the subterranean world being the last bastion of exploration now that satellites have mapped every inch of the Earth's surface.

Kevin is extremely thorough as he goes through the safety drill, but once underground he is at pains to explain the specific danger in this system where, in the past 10 years, 13 people have drowned, all in th same spot, where the river re-emerges into the light.

Although it looks as though the stream gently flows out of the cave into the "resurgence pool", a large part of the flow is sucked down into an invisible cave underneath the rock on which we are standing. The unwary caver, peering out at the daylight only metres away, might be tempted to swim out, even though the notices pinned to the walls explain the danger. A fateful error.

We begin to explore, and as the roof of the cave descends, we bend double, scrambling along the water's edge, our headtorches illuminating the boulders and shingle. The river here spreads out sideways creating a broad cave less than one and half metres high. As the flooor comes up to meet the ceiling, I have to crawl on my stomach, my head cocked sideways so I can illuminate the path ahead. The temperature in caves is usually around 9C, so my feet and hands are wet but not cold.

The Porth y Ogof system is not complex but it is easy to get disoriented. We come to a space where we can stand and look up at one of the potholes we had looked down into from the surface. Later we come to the Maze, endless rabbit holdes that lead back on themselves or to nowhere. The sound of rushing streams, mixed with the scraping of clothes against the grit and rock, is never far away. Besides your own voices this is all you will hear.

Kevin announces we have reached the Drain. The hole in the rock he is sitting on is the way in. I lower myself into the stream flowing through the tunnel below and crawl 20 metres through icy, fast-flowing water.

The Letterbox is ahead. Here, the tunnel is quite wide but so low that we have to wriggle completely flat, head to one side, keeping arms ahead at all times, see-sawing horizontally with arms and legs throught this crack in the rock. Thirty metres ahead, the crack narrows so that at the end you disappear through the Letterbox slit. I stand up and find myself back in the space where we had looked up to see the porhole entrance of a few hours before. I have come through a gap that, when I had been shown it from the other side as the way in, I had scoffed and thought: "No way." I had come from the fourth dimension – the inside.

Many cavers cite the disorientation and timelessness of exploring the underwold as one of its great attractions. It is; that and the sounds of water flowing, the beauty of the dark, and of the rock formations. I for one will be back for more.

Laura Ivill caved at Porth y Ogof, Brecon, Powys, with instructor/guide Kevin Walker (mountain-activities.com)