Did a Welsh Prince, Madoc ap Owain Gwynedd, discover America 300 years before Columbus? Queen Elizabeth I used the legend to justify her claim to America over that of Philip II of Spain. And even as late as the 18th century at least 15 Indian tribes were identified as Welsh - descendants of the Madoc expedition. John Evans, a young Welsh minister, in quest of Welsh Indians in 1796, became the first white man to reach the Mandans, whose descendants believe the tribe was brought across the Great Water by Lone Man - who was white! In this programme, filmed in America, Professor Gwyn Williams of University College, Cardiff, examines the Madoc legend.