Definitive account of the cultural and political impact on Wales of the flooding of the Tryweryn Valley. The failure of the nation to block the move politically led to increased Welsh national consciousness and to a period of militant activism which eventually led to the process of devolution.

Cofnod arbennig o effaith diwylliannol a gwleidyddol boddi Cwm Celyn ar Gyrmu. Arweiniodd methiant y genedl i rwystro codi'r argae trwy ddulliau gwleidyddol ar ymdeimlad cynyddol o hunaniaeth cenedlaethol ac at gyfnod o ymgyrchu milwriaethus a heddychlon dwys, a arweiniodd, yn y pen draw, at y broses o ddatganoli.