The Tennant Canal lock into King's Dock, Swansea Docks, was still in use in the early twentieth century but went out of use when this part of the docklands was subsequently re-developed. The lock is shown on the OS 25-inch plan 3rd edition having superseded an earlier lock, with canal branch, into neighbouring Prince of Wales Dock (shown on the 2nd edition plan).
Although the lock is no longer visible its substructure, with that of the adjacent canal cut, will still be intact beneath the surface of more recent developments.

David Leighton, RCAHMW, 29 July 2010