Plot: Matt Baker and Charlotte Smith are in Kielder in Northumberland to explore some of the 250 square miles of England’s largest forest. Charlotte discovers how this man-made landscape supplies a quarter of England’s timber - from the joists in your house to the chair you sit on - and heads to a ‘rock festival’ as Northumberland Wildlife Trust celebrates its 50th anniversary by revealing secrets going back millions of years that are hidden in the stones that shape this landscape