“Honestly, I’m just here to stop anyone dying, so I’m succeeding whatever you do.”

Not the most reassuring thing ever said at the top of a pitch. But at Merlin Mine on Tuesday, with Jacob leading his first SRT trip and Tim there to make sure nobody needed rescuing, it told you everything you needed to know about the evening ahead.

Tim ran a quick SRT refresher at the surface before anyone went near the edge. Descenders, cow’s tails, the basics. He then clipped a rope to a tree, decided to test it by hanging off a branch he’d already decided wasn’t safe, and nearly ended up on the floor. “God, I can’t believe I did that. I almost had a first aid incident. Would not recommend.”

Nobody was injured. Tim’s judgment was the only casualty.

Jacob’s wife Maura descended first, tucked under an overhang at the base, and held the rope from below. Rachel went next (her fourth or fifth time doing SRT underground, and looking like it). Matt followed. Then Justin, on his first ever SRT descent in a cave.

Everyone got down. Everyone got their descenders threaded, their cow’s tails off, their weight into the harness. The pitch is about 10 metres and the evening was warm enough that the usual underground chill was a relief.

At the bottom, Jacob gave the group a choice. Justin didn’t hesitate. “I’d like to explore because I’ve not been in this one before.”

The Grotto Chamber splits in about five directions. Tim’s advice before they scattered: “Prepare to be underwhelmed.”

He was half right. Matt climbed up to the prettiest section of the mine and found tiny stalactites. “Were they incredibly beautiful?” someone asked. “Yeah, a bit like these ones,” Matt said, gesturing at the mud.

Justin vanished up a side passage. “Have you found any caves?” came the shout. “Er, yeah,” floated back from somewhere above.

Rachel scrambled up a climb with people spotting from below. She made it look comfortable.

Up one of the climbs, tree roots pushed down through the ceiling, threading into the rock. “That bit up there feels like a natural cave and the rest of it’s all mine,” someone said. They had a point. The roots were the one place Merlin stopped feeling like a mine and started feeling like something older.

From the Grotto they headed into the main adit, past the old lead stope where you can look up and see where miners carved the rock out above you. Then through to the echo tube, where the acoustics demanded testing. Obviously.

Back at the pitch, ascending. Matt flew up. Rachel ground it out with focus. Justin attacked the rope with enthusiasm, if not grace. Everyone got up.

Jacob and Tim had both brought foot ascenders they’d never used before. “Both me and Jacob are trialling a piece of kit we don’t know how to use,” Tim announced. “We should breathe confidence.”

Confidence was not what they breathed. But it worked, mostly.

At the cars, Tim asked what everyone’s favourite bits were. Matt didn’t think long. “Exploring. It reminds me of being a kid in the woods.”

When you’re picking a direction in a chamber just because you can, climbing up a wall to see what’s on the other side, shouting back “Er, yeah” when someone asks if you’ve found anything, it does feel like that. Just you, some rocks, some mud, and whatever your face does when you scramble up to something and have no idea what’s there.