In 1878, a branch line was laid to Sudbrook, to support the works for construction of the new Severn Tunnel. One of the main tasks of this line was to deliver coal for the pumping engines needed to drain the tunnel workings. Even after the long-delayed tunnel opened in 1886, on the South Wales Main Line, this coal traffic remained the major reason for keeping this branch in service. By 1925, the busier traffic on the main line had led to an expansion of the junction with a head siding. Further sidings were provided to the north of the running lines, on the town side. These were well to the east of where the station is today.