Scotland in the early Middle Ages, between the end of Roman authority in southern and central Britain from around 400 and the rise of the kingdom of Alba in 900, was divided into a series of kingdoms. Of these the four most important to emerge were the Picts, the Scots of Dál Riata, the Britons of Alt Clut and the Anglian kingdom of Bernicia. After the arrival of the Vikings in the late 8th century, Scandinavian rulers and colonies were established along parts of the coasts and in the islands. In the 9th century the Scots and Picts were combined under the House of Alpin to form a single kingdom which formed the basis of the kingdom of Scotland.