Fiona Bruceand the team roll out their 40th anniversary tour as they scour the country in search of hidden treasures. The magnificent Castle Howard in Yorkshire is their first stop as thousands of visitors raid their attics to bring in family heirlooms to show the experts. Objects brought to light suggest that, four decades on, there are plenty of unrecognised and valuable pieces still out there. A letter in which Darwin admits to making a mistake in The Origin of Species stuns book specialistClive Farahar. A diamond brooch draws gasps of delight as the owner is advised of the value. And could it really be a lost work by Renoir that art specialist Philip Mould ferrets out? There is also a very emotional meeting for Roadshow regular Ronnie Archer Morgan when he is vividly reminded of his most important childhood memory.