At Powderham Castle in Devon, antiques experts Will Axon and Mark Stacey find several treasures to take off to auction, including a shotgun case that belonged to a First World War hero and a pristine collection of Dinky toys. Plus, Paul Martin delves into the past of the castle, which has been home to the same family for more than 600 years, and uncovers a scandal that changed the course of that family's history