Creswell Crags
Where did swallows nest before buildings were erected? In search of an answer Derek Jones , in the company of ornithologist Cliff Davies and senior ranger Rogan Jenkinson , visits Creswell Crags , a narrow limestone gorge pitted with caves in which the remains of woolly rhinos, mammoths, cave hyenas and man were deposited 70,000 years ago.
Producer MICHAEL BRIGHT BBC Bristol
(Re-broadcast next Saturday)