They played an important role in World War II when the 35 ft. high Nant-y-Gro dam was used by the Dambusters to practise for the breaching of the dams in the Ruhr Valley.
They played an important role in World War II when the 35 ft. high Nant-y-Gro dam was used by Barnes_Wallis to test his idea of detonating explosives against a dam wall in order to breach it. These experiments culminated in the Dambusters breaching of the dams in the Ruhr Valley.