The “sleeper” picture this week is — or purports to be — a Degas. It’s a tiny, charming oil painting of a ballet dancer, but it is not included in the relevant bible of Degas’ works. A nice old gent whose father bought it in 1945 would love to know if it’s worth a few hundred pounds or, if it’s the real deal, half a million. Rakish art dealer Philip Mould and his gloriously named researcher Dr Bendor Grosvenor assist Bruce in tracing the truth.

The Hosts of the show take a llok at the history of three paintings bequeathed to the National Museum of Wales after their owner died in 1951. It was always thought that the paintings were by landscape artist JMW Turner, but only months after the museum took ownership, experts said that they were fakes.

Art detective Philip Mould has a reputation for finding sleepers; paintings that hide dark secrets. His most remarkable finds are pictures whose true authorship has been confused, masterpieces lost beneath years of dirt and over-painting. Although Philip is used to investigating other people's paintings, this time the tables are turned as Philip's own purchase is put under the microscope. With his keen-eyed researcher Bendor Grosvenor, Philip has bought a painting that he says could be the find of a lifetime; a work by our most important portrait painter, Sir Anthony Van Dyck, one which is worth a small fortune. The only problem is that, in order to prove it, he will have to remove later layers of paint to uncover the truth. "It's a bit like open heart surgery" says Philip, as the expensive and irreversible process begins. A thorough restoration is needed, and inches of canvas are cut away as an earlier image begins to appear. Fiona is not convinced, and insists that the work undergoes a thorough investigation and is authenticated by an independent Van Dyck expert. Will Philip's reputation and the painting make it to the end of the journey unscathed?