Every year, millions flock to the homes and gardens of one of Britain's most important cultural institutions: the National Trust. Behind closed doors, dedicated teams of conservators, volunteers, curators and other experts battle to keep our priceless heritage alive.

In this episode, an exquisite gallery made of seashells needs shoring up, a priceless Rubens is saved from falling down and an ancient Egyptian obelisk is cracking up.

A missing masterpiece - Penelope and Euriclea, by groundbreaking female artist Angelica Kauffman - returns to its stately home, the grand Palladianvilla Stourhead, after two centuries. Plus the search for the lost castle of Stourton and the scrapbooks revealing one man's mission to save English country houses.