agreement was reached with the rhymney railway to share the costs of construction for a extension from nantybwch to . where a junction was made with the rhymney's line to cardiff docks over which the l&nwr obtained running powers. the joint extension was opened for goods traffic on 1 august 1871 and to passengers on 2 october 1871. the agreement with the rhymney allowed the l&nwr to open a goods station at tyndall street in cardiff on 1 october 1875.