Penarth Dock opened in 1865 on the southern edge of
Cardiff Bay, at the mouth of the Ely. However, the nearest crossing over the river was a road bridge nearly a mile upstream at
Llandough. The operators of the dock, the
Taff Vale Railway Company, introduced a
chain ferry across to the northern bank of the Ely as a shortcut for both their workers (many of whom lived in Grangetown) and members of the public. However, the ferry was unable to run in bad weather—even sinking twice during storms—and as the docks continued to develop in importance a permanent crossing was considered necessary. The company submitted a bill to
Parliament in 1896 seeking permission for a number of new works, one of which was a tunnel beneath the river to replace the ferry. Construction began in July 1897 on a subway designed by George Sibbering, the company's chief engineer, with works overseen by Thomas Taylor, a contractor from
Pontypridd. The ramped entrances at either end were dug by hand but the majority of the route—325 yards of the subway's total length of 400 yards—was tunneled with a
Greathead shield, of the same design used for the
Central London Railway. The northern entrance was located at the southern end of Ferry Road in Grangetown (next to some large petroleum storage tanks owned by the Bear Creek Oil Company), while the southern entrance was next to the dockside Mission Church. The total cost of construction was between £25,000 and £26,000. The subway had a diameter of 10 feet 6 inches, with a usable footpath 6 feet wide, and 7 feet 6 inches of headroom. The tunnel ramped downwards relatively steeply from both entrances to its halfway point, with a gradient of 1 in 7. The interior was painted with a mixture of white enamel and granulated cork to prevent condensation, and lit with electric bulbs. Toll keepers oversaw
turnstiles at either entrance, charging pedestrians a penny for entry, cyclists two pence, and prams four pence; horses also reportedly used the subway. It also carried gas and water pipes, and hydraulic lines for coal-loading machinery in the docks, while water leaking in from outside the tunnel was pumped away through drains in the floor. A burst pipe on 4 August 1902 caused a flood and led to the subway's temporary closure. The subway was officially decommissioned in 1936 as part of the wider closure of Penarth Dock, and the toll keepers were removed, but it nevertheless remained open to pedestrians. It was repurposed as an air raid shelter during the
Second World War when the docks were requisitioned for the
U.S. Navy. == Present day ==