Overview
Trwyn Du Lighthouse, also called Penmon Lighthouse, was built in 1838 after the wreck of the Rothsay Castle and continuing danger in the channel between Anglesey and Puffin Island. James Walker designed its black-and-white tower on a tidal rock, and an unusual bell once sounded in fog. The active light marks the eastern entrance to the Menai Strait and frames one of Anglesey's best-known coastal views.
Why it was built
The loss of the Rothsay Castle in 1831 with heavy loss of life strengthened demands for a light at the dangerous channel. Trinity House chose the rock so ships could distinguish the passage between island, mainland and shoals.
People and work
James Walker designed the tower, and keepers maintained lamps, lenses and the fog bell in an exposed station reached at low tide or by boat. Local pilots and mariners depended on the signal when using the Menai Strait route.
How it changed
The light began in 1838, later gained stronger optics, electricity and automation. Resident keeping ended, and the fog bell was eventually removed from service, but modern equipment continues the same location-specific warning.
What survives
The striped tower, lantern, lower service structure and rock platform survive, with the words 'No Passage Landward' warning vessels from the wrong side. The tower remains active and cannot be treated simply as a picturesque abandoned monument.
Why it mattered
Trwyn Du mattered because one wreck helped turn known local danger into permanent public protection. Its warning inscription, light and former bell used sight, words and sound together to guide vessels through a route where a small error could be fatal.
History checked 15 August 2026 against the named sources below.
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