The Northern Isles, which consist of the two island groups of Shetland and Orkney, have been inhabited since prehistoric times but were formally annexed by the Norwegian king Harald Hårfagre in around 875 after he subdued the Vikings who used the islands as a base from which to raid Norway and Scotland.
21st June 1919: The German High Seas naval fleet is scuttled at Scapa Flow
21st June 2019