Comedian and actor Ben Miller makes a long-cherished personal journey in search of his Welsh ancestors, discovering a tale of heroism in WWI and a surprising family link to the White House.

Former athlete and Strictly Come Dancing competitor Iwan Thomas makes an emotional journey in search of his Welsh ancestry, where he learns of an ancestor's life on a grand country estate, and of his great-great-grandfather's spectacular rags-to-riches story and the fortunes he made and lost in his lifetime.