Countryfile heads to the wild, rugged and dramatic landscape of Northumberland. From its moorland to its coastline, its beauty belies violent times. It is a county where we first encountered a fearsome new threat brought in on the seas. Julia Bradbury unpicks the history of this ancient kingdom and she learns how it has also influenced the local dialect. Further in land and thousands of years later, an unknown soul was forging ahead with green energy. Matt Baker finds out how Lord William Armstrong, a pioneering Victorian, came up with a revolutionary plan to use the power of water to power his house. It was to become the first home-grown hydroelectric scheme in the world, and plans are afoot to fire it up again. Ellie Harrison finds out how the ancient art of willow spiling is helping to reinforce river banks in the Northumberland countryside. Elsewhere, Tom Heap finds out what impact the proposed new high speed rail link (HS2) is going to have on the countryside and the people living in it. And Adam travels to Shropshire to see how science is helping to protect and preserve the rare breed Hackney horse.