Out Stack or Oosta is the northernmost of the British Isles, lying immediately to the north of Muckle Flugga and 3 km north of the island of Unst. It is one of the North Isles of the Shetland Islands and lies within the Hermaness National Nature Reserve . Out Stack is little more than a rocky outcrop , and is uninhabited. It has been described as "the full stop at the end of Britain". In appearance it is like the top half of a christmas pudding protruding from the sea.