William Edwards (1719-1789), Welsh civil engineer, religious minister and self-taught stonemason. Edward's greatest achievement was the building of the Pontypridd Bridge over the River Taff in Wales in 1755. His first design, made of wood, was washed away by floods. The second, made of stone, collapsed during construction due to its weight. Edwards modified his third design to include six large cylindrical holes to minimise weight, which stands to this day. At 42.6 metres it was the world's longest single-span bridge when completed.