Yes, a real collectors item. The sump passage when it occasionally dries out does have quite a draught but the choke prior to the stream passage has probably collapsed and will require scaffolding.
The line of dolines you talk about probably lie above the main long passage within Ogof Fawr. This east/west strike passage is heading roughly towards the sump zone in Ogof Fechan but approximately 200 -300 metres away.
A grade 3 survey showing the ends of Ogof Fawr and Fechan has been...
Aluminium screwgate carabiner lost on through trip from old entrance series to Ogof Cnwc. Most probably lost at Trickle in the ear squeeze of old entrance series.
Thanks for its return.