"King of all England and Denmark and the Norwegians and of some of the Swedes" (Cnut's self-proclaimed title)
"Knut was exceptionally tall and strong, and the handsomest of men, all except for his nose, that was thin, high-set, and rather hooked. He had a fair complexion none-the-less, and a fine, thick head of hair. His eyes were better than those of other men, both the handsomer and the keener of their sight." (Knytlinga Saga)
In a sense, Cnut the Great was practically destined for greatness, if only because he came from a distinguished Danish royal family. Cnut's father was Sweyn Forkbeard, and his grandfather was Harald Bluetooth, both prominent and legendary kings of Denmark. Meanwhile, his mother was the widow of the Swedish king Erik the Victorious, the daughter of the Polish duke Mieszko, and a sister of the Polish king Boleslav Chrobry.
Thanks to his background and his own abilities, Cnut became the most prominent of the Danish kings of England (from 1016), but he was also, at times, king of Denmark (from 1018-1019), Norway (from 1028), and parts of Sweden (after 1026). During his reign, he united England, protected Denmark, and had a lot of influence throughout Scandinavia, a remarkable feat that he managed to accomplish through careful alliances and diplomacy, yet most often through direct force. For that reason, Cnut has been referred to as the greatest Anglo-Saxon king of England, despite the fact he wasn't actually Anglo-Saxon. His death in 1035 came shortly before the Norman conquest of England by William the Conqueror.
For centuries, the Vikings had been raiding throughout the region, including in the British Isles, and Cnut's campaigns represented the apex of that activity. Somewhat ironically, Cnut is one of the best-documented leaders of the Vikings, a civilization that fascinates people mostly because they still seem mysterious and different compared to their European counterparts.