Cave details
The cave and its related caves are collectively known as the Three Counties System. A very complex system with more entrances than any other British cave system (28 I think but there may be more). Most entrances require the negotiation of pitches, with some routes very tight. A river runs in the lowest level creating a sporting streamway while upper levels contain large decorated passageways. The RRCPC site has a description (in sections). Despite claims by the surveyors that the cave is now over 100 km long, their total actually comes closer to 75 km, giving Ogof Draenen a real shot at becomming the longest cave in Britain. However, since the Ireby - Notts system is known to be part of this system, and is almost connected to it already, this system would clearly be far longer than the known cave in the Draenen system.
It holds the dubious honor of having had more deaths than any other cave in UK or Ireland in modern caving, with a total of 12 (which will become 17 once Ireby - Notts is connected). This is due, in part, to the fact that there is so much passage length in the system, and that the cave is split into several smaller caves and potholes. It is followed very closely by the far shorter Porth yr Ogof, which has had 11 deaths, and a further 1 historical. In poorly recorded history, Dunmore Cave in County Kilkenny, Ireland, holds this undesirable record, with evidence of at least 44 deaths from a Viking massacre in 928 AD, and a further adult and foetus that may also relate to the massacre. The Three Counties System falls to joint second place with Porth yr Ogof.