....I have since learned not to clamber around on or near stones that have rockart on them.
But I'm still not sure that any damage would be caused, using your pic as an example. I'm afraid I don't see what's so reprehensible about doing what you did there. You didn't stand on the cupmark, or kick it, or chisel your name into it.
I know Resonox has used the "monkey see, monkey do" argument before, but if someone was to see this picture and do exactly what you did, what harm would be caused? I know it sounds like I'm labouring the point (I probably am), but really this is at the heart of this whole thread. What is it exactly that we are supposed to be "against" and what are we supposed to be "for"? Because it seems to me we're heading for a preserve- in-aspic approach that would mean no-one goes near anything. No more walking around Avebury (erosion alert), nothing. Which strikes me as the precise opposite of what JC was encouraging when he wrote TMA. Weren't we supposed to get out there and reclaim our prehistoric past?
Look everyone, there used to be a stone circle here, but no-one was allowed to see it and it fell into disrepair. Then after a hundred years, an enterprising builder went to Westminster and said, look, here's all this waste ground that no-one goes near, I can build 20,000 houses on it and reduce the housing shortage. And then there's all these hills around, with overgrown banks and ditches, no-one goes there either, prime building land that, nowhere near a floodplain.