Jeff Wade: 'Its size and grandeur encompassed us'

We started the day at a small pitch head left by the other team at the end of some fairly tight, meandering passageways. One member of our team, Rob, went on ahead putting the ropes in, while myself and the other member, Ali, mapped the passages around us.

In the distance, we could hear Rob drilling in the bolts, but after about an hour we heard the sounds of rocks falling in the distance. When we caught up with him, he told us he'd come across a big expanse at the end of the passage, but the entrance was at the top of a slope of gravel, with boulders the size of cars at the top. He had come back for a bit of moral support – he wasn't happy exploring it alone.

Ali went down after Rob and had a look at the bottom of this boulder collapse, to see if there was a way through. They could see something around the corner, but from where I was you couldn't make out anything, just an echo in the distance.

By that point, Rob had scared himself enough for one day and was ready for a break. I decided to take over from him, but instead of heading downwards I swung out and across to get to a ledge about 20m off the floor, from where I was able to land on top of the boulder slope. I wasn't sure if it was going to slide away beneath me, but I could see a black space and the cave roof going up into nothingness. I traversed into the chamber, secured the rope and beckoned to the others.

It had a rock the size of a transit van in the middle, and lovely orangery-brown walls. Its size and grandeur encompassed us as we shouted and hollared to try to figure out how big it was. But then we realised there was no way on.

It was 2am and we were exhausted – we'd been surviving on snacks and no sleep – so we turned back. It was so disappointing. When we reached the other team, the expedition leader, Rob Eavis, ran up to me and asked what we'd found. I just said: "It's ended."