The GWR converted its South Wales system to the standard gauge in 1872, although in the meantime there was increasing hostility among mineral traffic customers against the constraints of the broad gauge, such that the L&OR projected a long line from Brynmenin to Nantgarw on the Rhymney Railway in 1871. The project would have been extremely expensive, although the London and North Western Railway encouraged it and would no doubt have contributed to the cost in order to get the access. However the GWR was motivated by now to convert its South Wales system to the standard gauge, which it did in 1872, and nothing more was heard of the scheme to reach Nantgarw. As the broad gauge system was no longer in use in South Wales, the L&OR removed the third rail that had been provided for broad gauge vehicles.