 After the destruction of the first bridge over the fast flowing River Taff , William Edwards decided to design a much more radical 140 ft ( 43 m ) single @-@ arch bridge that would eliminate the possibility of debris destroying the bridge due to the flooding of the River Taff . The second bridge was built from 1748 , however two reports differ as to what actually happened during this second attempt to build the bridge . Thomas Morgan , contemporary of Edwards , said that " … when he ( William Edwards ) had almost finished the arch ; the centre timber work gave way and all fell to the bottom . " However , The National Library of Wales have a contemporary works known as the Plasybrain manuscript which says that , " Just after the first single arch was finished and before the centre was struck , a flood came and carried all away . " It is not clear which one of these two accounts is the accurate one , however it is clear that Edwards ' latest attempted to build a bridge cross the River Taff had yet again ended in failure . 
