Begun in 1945, the station promised and still delivers a surge of 'green' electricity to the national grid, but that free power was bought at a price; 21 men died during its building.
With the war just over, many men went straight from the front to join another army, busy tunnelling through the heart of Ben Vorlich. Incredibly, some of the tunnellers were German POWs.
The 'diggers' are seen here, enjoying a well-earned beer, after breaking through the last nine feet to link the top and bottom tunnels.
The scheme took five years to complete, and was opened by the Queen on October 18, 1950.