‘Cofiwch Dryweryn’ is an iconic image of modern Wales. It refers to the compulsory eviction of the village of Capel Celyn so the valley could be flooded by the new Tryweryn Reservoir, built to provide water to Liverpool. 
The phrase "Cofiwch Dryweryn" has itself become a prominent political slogan for Welsh nationalism appearing on T-shirts, banners and as replica murals.