Britain's Lost Masterpieces

Pollok House is a country house right in a Glasgow city park, owned by Glasgow City Council and looked after by the National Trust for Scotland. It has a collection of Spanish art, the legacy of the man who once owned the house, Sir William Stirling-Maxwell. Unfortunately, some of its treasures have been placed in storage due to a leaking roof and renovations. But could one of these displaced pictures be a priceless lost work by Rubens? The painting's subject is George Villiers, Duke of Buckingham, the gay lover of James VI of Scotland. While Bendor squares up to a rival portrait in Florence which claims to be the real Buckingham portrait by Rubens, Emma finds that Stirling-Maxwell had a secret family in Jamaica and that sugar and tobacco built Glasgow long before shipbuilding was its major industry.

Along with a hippo skeleton, a stuffed hedgehog and a log boat, Derby Museum has the best collection of Joseph Wright of Derby paintings in the world. Wright of Derby is one of the greatest English artists who ever lived. He painted the most astounding ‘birth of science' scenes, his landscapes and portraits are exquisite and he was inspired by the Industrial Revolution.

But can our team peel back layers of modern restoration on a mysterious landscape painting stuck in the Derby vaults to reveal another hidden masterpiece by Wright of Derby?

Carmarthenshire County Museum is a slice of history in itself. The building that houses it has been in continuous use since the 13th century, once a Bishop's palace it was where the Bible was first translated into Welsh. But could it also be home to some mysterious cases of mistaken identity and two lost paintings from the time of Charles II?

Dr Bendor Grosvenor and Emma Dabiri travel to Carmarthenshire to investigate two intriguing portraits of a local nobleman and his wife, the Earl and Countess of Carbery, possibly painted by the great Sir Peter Lely in the 17th century.

Yet all is not as it seems: Bendor has a hunch that one of the portraits is by another hand. Could the portrait of the Countess be a lost work by Mary Beale, Britain's first commercially successful female artist?

While Bendor gets to grips with the badly damaged portrait of the Earl, Emma traces the story of how he survived the Civil War, how Mary Beale was written out of the history books, and discovers how the cross-dressing men of the Rebecca Riots stormed Carmarthen.

Hospitalfield House in the fishing town of Arbroath on Scotland's east coast is a Victorian treasure trove.

The couple who owned this great house back in the 19th century were obsessed with the decorative arts, and Hospitalfield is full of ornate carved ceilings, sculpted fireplaces, exquisite plasterwork and stonework carved by master masons. It's still a place where artists work today and it has a fine picture collection.

Among the many Victorian paintings, could a mysterious 16th century portrait by one of the great Old Master artists lie waiting to be discovered?