Where can you find a hill that looks like an Inca monument but which is in fact an old nitroglycerin factory? The answer can be found in the Lee Valley, a green and watery wedge that grows and flows from Hertfordshire and Essex through northeast London to The River Thames. Occupying a liminal space between rural countryside and the industrial, the Lee Valley presents a surprising landscape - where nature has come back reclaim the monuments of an industrial past.

Helen Mark travels down the Lee Valley and its waterways to explore how for centuries it was a crucial thriving hub of industry before falling into decline until more recently experiencing regeneration of its natural spaces. She visits the Royal Gunpowder Mills, Kings Weir Cottage, Glasshouses, The Waterworks and the Lee Navigation to meet people who work on and live by the Lee Valley's historical waterways; people like Barbara the wife of one of the navigation's last weir-keepers.

Presenter: Helen Mark
Producer: Melanie Brown.