I remember standing on a very large rock at the bottom of the Drunk and Stupid series we were exploring in 161 (our big Austrian cave) when it grunted as it shifted and slid a short distance. In those few moments I suddenly I had a very clear mental image of just exactly how far underground I was, just exactly how difficult it would be to get me out if I was injured, and just exactly how unexplored and therefore still loose the place we were standing was. Far from a place of safety. It concentrated the mind wonderfully, I can tell you...