Llanddwyn Island


Llanddwyn is a tidal island, on the southern shore of Anglesey.  The peninsula is only cut off at the highest of tides. Most of the time it is accessible by the mainland.

Located near the southern end of the Menai Strait, it was an important shipping route for slate from Bangor, Caernarfon and Felinhelli.

Around 1823 two day marks were being used as navigation aids.  One of the towers, Twr Mawr was adapted from one of the towers, and a light was established on 1st February 1846. Its shape indicates that it may originally have served as a windmill, later modified to be used as a lighthouse.

Originally lit using six Argand lamps with reflectors, Twr Mawr was lit using a Fresnel lens from 1861 until 1975. Unusually, the light was displayed from the bottom of the tower, with the building providing accommodation for the keepers. 

Twr Bach

The lighthouse was discontinued in 1975 and the light was transferred to nearby Twr Bach.

Twr Bach lighthouse was built between 1800 to 1818.  The solar-powered light was installed in 1975 and displays a red or white light to indicate safe and dangerous passage.

The nearby cottages housed the pilots who guided ships into the Menai Strait. Two of the cottages were restored after they were discontinued, and one has an exhibition.


A lifeboat was also stationed here from 1840, manned by the pilots, as well as volunteers from Newborough. The Lifeboat was closed in 1903.

Llanddwyn Island featured in Demi Moore’s film Half Light, using Twr Mawr within the film.  The lower half of the tower was painted red and special effects turned it into a taller lighthouse! 

Llandwyn Island also featured in the BBC programme The 1900 Island, broadcast in 2019.

Cross and beacons
Twr MawrEstablished: 1846 Discontinued: 1975 Engineer: Tower Height: 11 metres Light Character: Range: Fog Signal: Elevation: Automated:
Twr BachEstablished: 1800s, Light added 1975 Discontinued: Engineer: Tower Height: Light Character: Fl W R 2.5 s Range: W 7 miles, R 4 miles Fog Signal: Elevation: 12 metres Automated: