Fiona Bruce and Philip Mould investigate more potentially valuable works of art. They begin with an 18th-century landscape that could be a lost work by of one of the biggest names in British art, Thomas Gainsborough. The painting has been in the family of owner Mark Cropper for generations and until the 1970s it was considered to be a Gainsborough. But then a valuation downgraded it and Mark's father tore off the Gainsborough label in disgust. Now Mark would love to be able to re-apply the Gainsborough plaque.