The World About Us S1970E19 - The Lost River of Gaping Gill

High up in the Pennines of north-west Yorkshire a river leaps down a notable hole called Gaping Gill and disappears into the limestone hill. A couple of miles away at Ingleborough Cave a river appears out of the earth: today, it is known that these two rivers are one and the same.
For over a year, teams of fanatical potholers have attempted to make what is perhaps the last great geographical discovery in Britain: by what secret passages and chambers does the Fell Beck find its tortuous way from Gaping Gill to Ingleborough Cave? Perhaps even more extraordinary, an ex-BBC man Syd Perou, with a hand camera and a few lights packed in ammunition boxes, has for 15 months filmed the search in appalling conditions.
To have been a caver down some passages with only an inch of air space between water and rock is a considerable achievement. To have filmed it is an astonishing feat.