By the end of the First World War the mysterious sudden death of elms was a common sight across Belgium and the Netherlands. Dutch researchers managed to elucidate the real culprit amidst rumours of drought or wartime gas poisoning. It was a fungus thought to originate from America, carried by a beetle and the disease rather unfairly gained its name Dutch elm disease. Diagnosis produced no cure and it soon advanced across the channel to Britain. Professor Kathy Willis talks to the head of Kew's arboretum, Tony Kirkham, on the disease's impact amidst complacency, and how the emergence of a vigorous new fungal strain was to completely transform the landscape during its peak in the 1970's. Now that the principle replacement for lost elms, ash, itself has fallen victim to the latest disease to hitch a ride on incoming nursery stock, Paul Smith, Head of Kew's Millennium Seed Bank, explains why this new disease could be easier to control. Producer Adrian Washbourne.