Flat Holm () is a Welsh island lying in the Bristol Channel approximately from Lavernock Point in the Vale of Glamorgan. It includes the most southerly point of Wales.
The island has a long history of occupation, dating at least from the Bronze Age. Religious uses include visits by disciples of Saint Cadoc in the 5th-6th century AD, and in 1835 it was the site of the foundation of the Bristol Channel Mission, which later became the Mission to Seafarers. A sanatorium for cholera patients was built in 1896 as the isolation hospital for the port of Cardiff. Guglielmo Marconi transmitted the first wireless signals over open sea from Flat Holm to Lavernock. Because of frequent shipwrecks, a lighthouse was built on the island, which was replaced by a Trinity House lighthouse in 1737. Because of its strategic position on the approaches to Bristol and Cardiff a series of gun emplacements, known as Flat Holm Battery, were built in the 1860s as part of a line of defences, known as Palmerston Forts. On the outbreak of World War II, the island was rearmed.
It forms part of the City and County of Cardiff and is now managed by Cardiff Council's Flat Holm Project Team and designated as a Local Nature Reserve, Site of Special Scientific Interest and a Special Protection Area, because of the maritime grassland and rare plants such as rock sea-lavender (Limonium binervosum) and wild leek (Allium ampeloprasum). The island also has significant breeding colonies of lesser black-backed gulls (Larus fuscus), herring gulls (Larus argentatus) and great black-backed gulls (Larus marinus). It is also home to slowworms (Anguis fragilis) with larger than usual blue markings.
History
Bronze Age
The first traces of human habitation of the island are from the late Bronze Age, 900 to 700 BC. A bronze axe head was discovered on the island in 1988, between the island's farmhouse and West Beach.
Sub-Roman
In the sub-Roman period of the 5th-6th century AD, it became a retreat for Saint Cadoc, who lived on the island as a hermit for seven years. His friend, Saint Gildas born in the Kingdom of Strathclyde but educated at the College of Theodosius (Cor Tewdws) in the Kingdom of Gwent, lived at the same time on nearby Steep Holm, and the two sometimes met up for prayers. Gildas eventually left the island to become Abbot of Glastonbury.
In June 1815, a Dr Thomas Turner visited Flat Holm in a small boat and was stranded for a week due to high winds. He discovered two Christian graves located close together in a field northeast of the island's present farmhouse; one grave had been opened and contained a male skeleton. The open grave's headstone was made of purbeck marble and engraved with a Celtic cross, but had since broken in two. A second disturbed grave, also marked with a headstone, was found to the southeast and contained a coffin constructed with iron bolts. Inside the coffin were two skeletons which had been doused in lime, indicating that the occupants had probably died from a contagious disease.
Middle Ages
Anglo-Saxons called the island Bradanreolice. Reolice derives from an Irish word meaning churchyard or graveyard, alluding to the belief that the island had religious significance as a place of burial to people at the time. However, the island's current English name of "Holm" comes from the Old Norse meaning "island in an estuary". Records indicate that a Viking fleet from the south of Brittany led by two earls, Ottir (Oter) and Hroald (possibly Ottir's king Ragnall), took refuge on the island following their defeat by the Saxons at Watchet.
The Anglo-Saxon Chronicle records that in 1067, Gytha Thorkelsdóttir, mother of Harold II, the last Anglo-Saxon king of England, stayed on the island before travelling to St Omer in France after the Norman conquest of England. After the invasion, Robert Fitzhamon formed the Shire of Glamorgan in Wales proper, with Cardiff Castle at the centre of his new domain. Flat Holm came within the parish boundary of St Mary's, one of Cardiff's two parish churches, and was kept as a hereditary property of the Norman Lords of Glamorgan.