Big Country tells the stories of the men and women who dedicate their lives to looking after Wales's National Parks in Pembrokeshire, Snowdonia and Brecon. A fifth of Wales is designated parkland - a breathing space for the people. Although these beautiful landscapes seem rugged and indestructible, they need care to survive. But who are the guardians that safeguard their future and protect them from threats, both man-made and environmental? This episode looks at the astonishing discoveries on the Castle Martin Firing range, which have brought excitement to the archaeological world. Wardens Jon and Sam in Brecon are still waiting for their bridge to arrive, and in Snowdonia, bat enthusiasts track down these nocturnal animals.