Emboldened by the success of the initial line, the company decided to build a more ambitious line from the Llanelly Dock to pits further to the north-east. The company changed its name at this time to the Llanelly Railway and Dock Company, by Act of 21 August 1835. This second line, separate from the Dafen line, opened as far as Pontardulais in 1839, extending to Duffryn and Cwmamman on 6 May 1840. In the following two years an eastward extension to pits in the Amman Valley was opened, and in 1842 a westward branch to the Great Mountain (Mynydd Mawr) was constructed.