Hidden Treasures of the National Trust

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 look at the teams who care for two luxurious mansions on the edge of London that have long played a pivotal role in society through the lavish parties and country house weekends they hosted: Cliveden House, the former home of Nancy Astor, and Polesden Lacey, the weekend retreat of the heir to the McEwan's brewing empire, Margaret Greville.

Meanwhile, an Edwardian clock tower is running out of time, and a Renaissance balustrade needs an intervention.

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.

A look at the teams who care for the some of the most important legacies left to the National Trust, from an aristocrat's hoard of priceless treasures to the modest family home filled with everyday objects from 1920s middle-class life.

Behind the leaded windows of the Cambridgeshire mansion Anglesey Abbey lies one of the National Trust's most extraordinary collections: 15,000 objects amassed during the lifetime of one man - Urban Huttleston Rogers Broughton, 1st Baron Fairhaven.

Meanwhile, in Worksop, a modest semi-detached family home is a perfectly preserved time-capsule of early 20th century life. And the team that care for the Trust's largest fashion collection, based at Killerton House in Devon, are selecting pieces to display in their annual exhibition - no easy task with over 20,000 items to choose from.

A look at the teams caring for two houses which served as launchpads for the soaring ambition of their owners.

Saltram House, in south Devon, was once the country seat of the Parker family. But its 18th-century carpet, designed by architect and interior designer Robert Adam and knotted by Axminster founder Thomas Whitty - is in dire need of restoration, leading to a protective re-weave of the original design by Axminster themselves.

Meanwhile, the house's 18th-century occupant Theresa Parker is also receiving some essential treatment: renowned portraitist Joshua Reynolds captured the spirit of a young Theresa in a once-striking portrait that's now in need of reviving before it goes on loan for a major exhibition of Reynold's work.

Nestled in the Chilterns, Hughenden Manor is a house that helped propel Benjamin Disraeli to the very peak of power. But in the grounds, the once gloriously golden carriage gates that welcomed his guests are in need of restoration. Blacksmith David takes on the daunting task with the help of blood, sweat and a wedge of gold leaf.

At Chirk Castle, a very rare, full-length portrait of a servant from the 18th century reveals its secrets. And in Oxburgh Hall, on the edge of the Norfolk fenlands, two rare hidden treasures - a rat's nest found under floorboards containing scraps of clothes that could be centuries old, and an overlooked portrait tucked away under the stairs - are brought back into the light.