How Nant-y-Gro dam helped the Dambusters

The following is an account of an unexpected site visit by the author to Nant-y-Gro dam. This masonry dam in the Elan Valley was built in the late 1800s, to supply water to the worker's village during construction of the larger Elan Valley dams. In 1942, the dam was used by the British government, under the supervision of Barnes Wallis, to carry out early experiments during the development of the ‘bouncing bombs’ used for the Dambuster raids in the Ruhr Valley in Germany.