We have been contacted by the Craven Pothole Club. During a recent trip into Gaping Gill via Bar Pot, some of their members and guests had some concerning incidents.
Firstly, while in the Main Chamber, a very large cobble crashed down only metres from them despite no surface stream flowing. It is considered possible that this was thrown down.
Secondly on their way out, they found that the karabiner in one of the anchors in the traverse line leading outwards from the first pitch (the first karabiner below the surface) had been taken and the rope poorly tied back into the anchor with two overhand knots (which would almost certainly not bear weight... see photo).
Whether the two incidents are related is unknown.
Hopefully this is just a one-off occurrance; it is certainly not something we encounter often. However it would be prudent to take extra care around shafts open to the surface, particularly on well travelled areas (Gaping Gill, Alum Pot), and to consider performing surface or near-surface rigging with rather less desirable maillions rather than valuable krabs (and to consider spannering them up). While the loss of a krab is annoying in terms of value, the consequences of reliance on a traverse line which has been tampered with could be far more severe.