He had been harrying England on and off for 20 years, attacks which intensified after his sister had been among the victims in the St. Brice's Day Massacre of Anglo-Danes in 1002. In 1013, “before August”, accompanied by his son, Canute, he invaded. He arrived at Sandwich before sailing north, laying waste parts of the south-east and east coast before raiding deep into the heart of England via the Humber and River Trent and setting up a base at Gainsborough, Lincolnshire.
He was quickly recognised as king by most of the residents of the Danelaw. Now, sure of local support he moved south. Oxford and Winchester surrendered immediately, most of England shortly after. London held out for a number of months but submitted at the end of the year. King Ethelred the Unready fled to his wife’s family in Normandy. Sweyn died about five weeks later, on February 3, 1014. His son, Canute, who had made a name for himself for cruelty and treachery, was too inexperienced to build on his father’s unconsolidated successes in England and sailed home – though not without a deal of pillage and other unpleasantness before he left the shores.
Ethelred was able to resume his reign.
‘’”Anglo-Saxon Chronicle”’’ trans. Anne Savage 1984 p157 ‘’”The Oxford Companion to British History”’’ 1997 p905