Trustee Tim, Even if the PDCMG was "most representative and democratic cave management group in the UK" it is in in a pretty small group isn't it? OFD, DYO, MLCMG that I can think of in Wales, Peak Cavern perhaps?
As you know PDCMG was set up to represent the clubs involved in active exploration in 1996, so was skewed away from more recreational and non-local clubs; this bias may have reduced over the years (in spite of some blatant attempts at gerrymandering that I was witness to) but I suspect that andrewmc's view that "the current system doesn't seem work for the larger caving community" might well win a vote organised (heaven forbid!) amongst the BCA membership. His point that "access bodies should negotiate to improve access for cavers, not manage it for land owners" is very pertinent, albeit they will, by their very name, manage access (and more), but with the emphasis being on the responsible use of the cave (whereas landowners - and some elements in statutory authorities - might well prefer there was no cave at all).
On Twll Du itself, the photo demonstrates clearly that the entrance is not on the tramway itself (albeit within the - perhaps somewhat arbitrary? - boundaries laid down - rather negligently, it appears, near Garnddyrys, as RichardB1983 has alluded to) and has not damaged any abutment. It will be interested to see what precisely Cadw adjudges the damage to be - perhaps to the edge of its levelled base, which might even have filled in an open cave entrance, perhaps? I walked past the entrance in August and it was quite invisible, hidden by gorse and other vegetation, but that has clearly now gone.
I was not familiar with the meaning of 'a community resolution' - here is a local links to check for yourself its meaning and implication: http://www.connectgwent.org.uk/what-is-a-crime/anti-social-behaviour/
Whether or not any offenders are identified, a resolution is clearly required in terms of 'securing' the site for the future. Just replacing some rocks and turfing over could eventually restore the staus quo, but be open to the threat of disturbance which has kept Drws Cefn open. Capping with concrete or the like would be unnecessarily obtrusive and not, I think, in keeping with an ancient monument. I hope that the PDCMG and other interested bodies (Cambrian CC, local clubs and amenity groups, NRW, local authority planners...) will be willing, able, and allowed the opportunity to persuade Cadw and Pwlldu Conservation that there is a case for leaving an accessible but discrete (as it was, apparently for almost a year) entrance for cavers (and bats? who knows?), secure from misuse: all cavers I know who have been down say it is by far the most impressive of Draenen's entrances so far - as soon as you get inside... It might even allow the PDCMG to make the local landowner happy again - it's a long way from his house, where the view of cavers has annoyed him in the past, and not on his private access land...