An island in the Firth of Forth off the south coast of Fife opposite Braefoot Bay, separated from the mainland by a stretch of water known as Mortimer's Deep.
It was the home of a religious community linked with St Colm or St Columba, the 6th-century abbot of Iona. King Alexander I of Scotland was storm-bound on the island for three days in 1123 and, in recognition of the shelter given to him by the hermits, promised to establish a monastic settlement in honour of St. Columba. Though the king died before the promise could be fulfilled, his brother David I later founded a priory here for monks of the Augustinian order. This was eventually erected into an abbey in 1223.
The well-preserved abbey and ruins of the 9th-century hermits' cell attract visitors to the island which can be approached by boat from Aberdour and South Queensferry.