William's letters to his daughter Suzanna are held by the Library Company of Philadelphia and stored at the Historical Society of Pennsylvania. These letters show that the factory was bought by William to keep Lewis active while the latter was suffering from gout. The highlight of this period of production of Swansea Pottery was the opening by Lewis Weston Dillwyn and George Haynes of the Cambrian Company, the Swansea Potteries London Warehouse on Fleet Street which operated between 1806 and 1807.[2] In 1814 the pottery took over the workforce of the Nantgarw Pottery and began to make porcelain.
In 1817 he temporarily retired from the pottery. In 1818 he became High Sheriff of Glamorgan and was elected to the First Reformed Parliament in 1834 as MP for Glamorganshire. He bought Sketty Hall near Swansea and was elected Mayor of Swansea in 1839.[3] Dillwyn was also one of the founders of the Royal Institution of South Wales and its first President, and in 1840 he published a short history of Swansea.