Leaving Strumble Head behind, vessels enter Cardigan Bay, where in the 1890s a lightship was stationed which is no longer in use. The next headland encountered is the Lleyn Peninsula of Caernavonshire with the small island of Bardsey separated from the mainland by the Bardsey Sound. The island, some 2 miles long by ½ mile wide, is surrounded by outcrops of sharp rocks.

In the sixth century Bardsey was a refuge for the Celts who sought sanctuary from the bloodthirsty Saxons. Only the ruins of the Abbey of St. Mary remain, but the sanctity of its patron, St Dolmers, who died there in 612 made the Abbey famous all over Britain. The remains of many venerable monks were conveyed to the island to be buried, and acres of graves record tales of pious and laborious lives.

Bardsey Lighthouse stands on the southerly tip of the island and gives a guide to vessels in passage through St George's Channel and the Irish Sea. The building was erected by Trinity House in 1821 at a cost of £5,470 12s 6d plus a further £2,950 16s 7d for the lantern.

The lighthouse tower is unusual in being square in plan. It is striped in red and white horizontal bands.

In 1987 the Lighthouse was converted to automatic operation and up until 1995 was monitored from the Trinity House Area Control Station at Holyhead. It is now monitored from the Trinity House Depot at Harwich with a local part-time attendant carrying out routine maintenance.