See Ogof Ffynnon Ddu 1 for description relating to OFD as a whole.
The cave was first found by quarrying and then explored by the Dragon Group in 1937. The cave was re-opened by SWCC in 1957. It as then a medium sized cave with about 900 metres of passage. Subsequent exploration led to it being connected to OFD II in 1966 by Clive Jones & SWCC.
SSSI: 0099 Ogof Ffynnon Ddu (Mixed)
SWCC nl 44, pp.12-13, 1963, Bill Birchenough, Cwm Dwr Jama [breaktrough; radio location; dye test]
See Ogof Ffynnon Ddu 1 for bibliography for OFD as a whole