In the last of his current series celebrating Clever Trees Richard Uridge visits the National Arboretum at Westonbirt in Gloucestershire, England – with 18,000 specimens a veritable tree university – and talks to the trees.

In the fourth of his programmes on Clever Trees Richard Uridge visits the Lost Gardens of Heligan in Cornwall, England, where he finds a relative of the culinary bay that’s so potent it can give you a headache and another trees that’s smart enough to provide the cure.