Ingleborough is limestone – or karst – country.  It is world famous for its caves.   Part Five features Avelina Wright from the local Cave Rescue Organisation.  ‘We don’t only pull humans out of holes,’ she says.  Such was the pull of the caves for Lincolnshire woman Leann Rennie, she upped sticks and moved to the area.   ‘There’s everything here that adventurous people like,’ she says.  Her husband, Tam Rennie, also speaks of caving, while also giving an insight into his day job as signalman at Blea Moor on the Settle-Carlisle railway.  ‘You don’t have to talk to anyone, it’s just bells,’ he says, glorying in the isolation.  Presented by Andrew Fagg and Anna Greenwood.