I was part of a group visiting Masson Cavern through the front door on Thursday night, but when we went through the gate into the back workings we started finding very fresh (i.e. still wet) paint markings at various points. Quite apart from the general comment among my group to the effect that if you can't navigate around Masson without the aid of paint markings you shouldn't be in there without a guide, the whole site is a SSSI and daubing paint around in them is an offence.
I'll let Dave Webb know about this so DCA can organise a clean-up once it's dried, and I'll also suggest notices inside the back entrances. If anyone does come across people daubing paint underground please tell them this is not on, and they should use cairns/floormarks if they need to make waymarkers underground.
Follow the horses, Johnny my laddie, follow the horses canny lad-oh!