Plot: Kate Adie argues for Ravensworth Castle in Gateshead, a 14th-century building with additions spanning over 500 years; in contrast historian Michael Wood advocates the preservation of the newest building featured in the series, the WW2 PoW Camp at Harperley in County Durham; and gardening expert Rachel De Thame speaks up for a folly and glasshouse at Wentworth House in Barnsley.