Volume Ten - Pre-Victorian to the Present Day - Even more aspects - Penarth Dock and Llandough Fields Reclamation Report : 1989 . . .

Access between the Penarth Dock and the Tidal Harbour was by a chain ferry, dependent on the state of the tides, or by road, on the payment of a toll. However, as the dock became busier an alternative crossing was provided by the construction of a pedestrian subway under the River Ely. The southern end of the subway, which was closed in 1963, is under the access road along the river bank, opposite the east end of the dock.

The demand for coal was unabated and by 1880 an Act was obtained by the Penarth Harbour and Docks Co. to enlarge the dock, adding 870 ft to its length, and the construction of four more coal tips. The extension was completed in 1884. Construction details of the inclined walls to the south side of the dock are understood to have been the same as for the original dock. However, on the north side of the dock, instead of adopting voided masonry with arches, the construction of the extension was changed to solid masonry with 4 metre thick walls, with an exposed face 14 metres high.

The Penarth Dock reached peak output during the First World War, handling nearly 3,400,000 tons in 1916. However, after fifty years of expansion, demand no longer increased and the Penarth Dock then started to decline.

After the first World War there was a brief boom in trade, but demand for Welsh steam coal lessened. However, the future of the dock appeared to be assured when the Taff Vale Railway was absorbed into the Great Western Railway in 1922. This was not to be the case. Dockers were made redundant in 1931 and a "temporary" closure notice in 1936 stated that vessels would not be admitted into the dock for loading or discharge, but that ships could enter the dock for repairs at the pontoon, constructed in the 1910's for that purpose.

The dock was reopened and became busy again during the Second World War, when the north side was remodelled to cater for the handling of stores and equipment by electrically operated cranes. On the south side four remaining coal hoists were made serviceable. After the war the dock was again closed "temporarily" and many railway lines removed. Few coal hoists remained, with one crane, and the dock was used by the Reserve Fleet for the laying up of frigates.