The team face a daunting challenge as they search for lost masterpieces in Britain's public art collections. To focus their research they look to the Your Paintings online records, where many thousands of oil paintings are listed - 17,000 of them recorded as 'artist unknown'. From these Philip and Bendor believe they have identified several important yet previously unidentified works by Thomas Gainsborough - but can they prove it?

A handsome portrait of Joseph Gape, mayor of St Albans in the 18th century, languishes in a backroom of the city's museum. The identity of the artist who painted it is unknown - but Bendor thinks it is a Gainsborough that dates back to his days as Britain's foremost high society portrait painter. The team thinks there are telling signs in the way the man is dressed and the unusual shape of the frame - but they'll need to convince the world's leading Gainsborough expert.

An even tougher challenge is posed by Imaginary Landscape, held in London's Courtauld Institute. Philip thinks it is also an important lost work - a rare, late Gainsborough landscape, painted when the artist was experimenting with dreamlike scenes. But would Gainsborough really have executed it on paper rather than canvas, and why is conservationist Aviva Burnstock troubled by a distinctive blue pigment?

Philip made his name in the art world with his Gainsborough discoveries and his reputation is on the line as decision time looms. Show less