'The Thirteenth Hour' by Stephen Grenfell
Produced by Alan Burgess
With four friends Harry Thierens set out to penetrate farther into Isaac's Cave in Cleeve Hill, Gloucestershire, than any other pot-holer had previously done. Now, for thirteen hours, he had lain trapped. A man he had never met -Patrick Hamlett-supported by scores of other rescuers, worked desperately under appalling conditions to attempt to free the man before it was too late.