Doubts had already been cast over the safety of Welsh hydroelectric dams built in the early years of the century to supply aluminium smelters. In 1924, most of the earthfill air face on the Cowlyd dam washed away, and catastrophe was only avoided because the concrete core continued to support the water face section of the embankment. A year later, 16 people died when the Eigiau and Coedty dams in the next valley failed in succession and more than 1M.m3 of water swamped the village of Dolgarrog.
This tragedy could not compare with the 1864 Dale Dyke dam collapse which killed 250 people in Sheffield but, coupled with the failure in 1925 of the small Skelmorlie Dam near Glasgow in which three people died, it produced an enormous public outcry.
The report into the Dale Dyke disaster was resurrected and its main recommendation - that all existing dams should be subject to regular inspection and that all new dams should be designed only by engineers - was eventually implemented by the 1930 Reservoirs (Safety Provisions) Act.
Said to be the first such legislation anywhere in the world, the Act took many years to implement and, as late as the 1960s, there were still major dams in the UK which had never been inspected. Nevertheless, no finished dam has failed since - and only the sudden collapse of the partially- complete earthfill Carsington dam in 1980 mars the record.