King Sweyn did not take Thorkell's change of sides too well. Revenge for this act probably played a role in Sweyn's attack in 1013. Æthelred left for Normandy with his wife and children, and the throne was free for Sweyn to take. 'London submitted to Sweyn, and the Chronicle says that all the English received him as full king'

The reign of Sweyn was only a short intermezzo, though. He died on 2 February 1014. His kingdoms were divided between his two sons. While Harold ascended the throne of Denmark, Cnut was supposed to become king of the English. But a rebellion forced Cnut to leave for Denmark, accompanied by Thorkell, and Æthelred was asked to return. But Cnut was not so easily put off. With the help of his brother Harald, he raised 'a large fleet for an invasion to regain the crown of England. Various sources have numbered this fleet between two hundred and one thousand ships. The lowest estimate comes from the earliest source and is likely to

be the most accurate, indicating an invasion force of over ten thousand men. Cnut was joined by his Norwegian brother-in-law, Earl Erik of Lade, whose long experience in warfare and government made him an ideal advisor for the inexperienced young prince. Just before leaving, they were joined by Thorkell...' Shortly after their arrival in 1015, Cnut's army was joined by Eadric Streona with forty ships. Cnut soon controlled Wessex. Æthelred lay dying in London, and his son Edmund Ironside went to Northumbria to form an alliance with Earl Uhtred. Cnut had Uhtred murdered on the advice of Eadric. 'The Northumbrians, none the less, stayed with Cnut and accepted his nominee, Eric, as their earl.' Æthelred died in spring 1016 and his son Edmund was declared king. Eadric Streona ran over to Edmund, which turned out to be a mistake. Edmund was decisively defeated by Cnut later that year at Ashingdon in Essex. Edmund himself could flee. Since the battle had brought heavy losses on both sides, Cnut negotiated with Edmund and the kingdom was divided. Edmund remained king of Wessex, while Cnut received the country north of the Thames. This situation did not last long, however. Edmund died on November, 1016, and Cnut became king of England. Cnut right away had Eadred, who had once more changed sides at the battle of Ashingdon, executed, along with several important Anglo-Saxon nobles.

'For the English people, King Cnut's reign from 1017 to 1035 was much like the month of March, "in like a lion and out like a lamb". Crowned in the turmoil of war and conquest, Cnut quickly established an era of peace and prosperity.' Cnut married Æthelred's widow, the daughter of Richard, Duke of Normandy, and both agreed that the common children of Cnut and Emma should have priority in the line for the English throne. 'With his kingdom free from attack from Normandy, Cnut felt secure enough to send most of his army home in 1018. The fleet was paid off with a huge Danegeld of 72,000 pounds of silver collected from throughout the country and an additional 10,500 pounds from London. Cnut retained forty ships for his personal body guard and to serve as the nucleus of a defence force. In the same year, at a national assembly at Oxford, both the Danes and English in the kingdom agreed to accept the laws of King Edgar as the foundation of their legal relationships. These laws were later drafted into a legal code by Archbishop Wulfstan. At this point, Cnut's reign as an English king effectively began.'

Cnut's reign was peaceful and well-structured. 'By the time of his death in 1035, Cnut was recognised as an equal by the Holy Roman Emperor and had negotiated with the Pope as a Christian monarch.' England became for a short while part of a northern empire including Denmark, Norway, and part of Sweden. He brought major improvements to all his people, such as the high level of minting of England to Denmark, or better education outside monasteries to England. But his achievements began to crumble soon after his death. He had two sons with Emma, and was succeeded by the first of these two, Harold Harefoot, in 1035. But Harold died in 1040, and his brother Harthacnut in 1042. Harthacnut was followed by Æthelred's son Edward the Confessor, and the English throne was thus once more in Anglo-Saxon hands.