It said simply .... Thanks from the Liverpool Corporation.
Lake Vyrnwy was created during the 1880s in order to provide a storage reservoir of safe water for the city of Liverpool. The river Vyrnwy was blocked up by a huge masonry dam, the first of its kind to be built in Britain. As the water built up behind the dam, the valley and the village of Llanwddyn were flooded. The dam measures 26 metres (84 feet) from the bed of the lake to the sill for the overflow, it is 357 metres (1172 feet) high and the base is 36.5 metres (120 feet) wide. The water left the lake along an aqueduct or pipeline at the start of its journey to Liverpool, some 70 miles away. These photographs show the construction of the dam and aqueduct between 1881 and 1889.
Above is a picture of the village before it was drowned, just so the English can drink.