In 1013 Cnut, younger son of Sweyn Forkbeard of Denmark, accompanied his father during his invasion of England, when they forced King Æthelred II (the Unready) into exile in Normandy.
On the death of Sweyn on 3rd Feb 1014, Æthelred II regained the English throne, while Cnut inherited the Danish throne.
By 1016 Cnut was fighting in England, where the throne had passed to Edmund II earlier that year. Cnut won a decisive victory over Edmund at Ashingdon on 18th Oct 1016 and shortly afterwards became king of all England.
He was crowned in 1017 and in the same year he divided his new kingdom into four earldoms and married Æthelred's widow Emma of Normandy in order to help legitimize his reign. He already had a "temporary" wife, Ælfgifu of Northampton, whom he sent to Denmark as to reign there as his queen. By carefully selecting his advisors he became very well placed to command loyalty from both the Danish and the English parts of England and was able to revive English law and government. He went on pilgrimage to Rome in 1027 and his prestige was high in Europe.
After his death the throne reverted to the English line.
Here is a penny from the reign of Cnut I
This Sceptered Isle
Cnut, The Viking King of England
Canute, King of the English: On Heriots and Reliefs
Life of Canute
Monetary History
"The Reign of Cnut", Ed. Alexander Rumble, at Amazon UK for £21.99 or Amazon USA
"Cnut: the Danes in England in the Early Eleventh Century", M. K. Lawson, at Amazon UK for £17.99 or Amazon USA
"Queen Emma and Queen Edith: Queenship and Women's Power in Eleventh-Century England", Pauline Stafford, at Amazon USA
Queen Emma And The Vikings: A History of Power, Love, And Greed In Eleventh-Century England, at Amazon USA
King Canute: Lessons from a great Dane - 29/09/00
Predecessor: King Edmund II
Successor: Harald I
Father: Sweyn