The Monarch Isles (57°31'N 7°38'W) some five miles west of North Uist, in the Outer Hebrides, are a collection of little more than sand dunes on a rocky base, rising to only 60 feet above the Atlantic waves. Also known by the old Norse name of Heisker, the islands were inhabited with a human history going back at least before AD1000, and had a population of probably only a hundred or so. The islands were finally abandoned in 1931 except for the lighthouse keepers who stayed till the light was automated in 1942. Its subsequent lack of human habitation has allowed the grey seal population to flourish to its present size of around 100,000 seals, some two-thirds of the total UK grey seal population. The islands are a National Nature Reserve and European Special Area of Conservation for marine environments.