Harold Harefoot, son of Cnut by Ælfgifu of Northampton, ruled England first as regent and then as King Harold I (1035–1040) while his half-brother Harthacnut was held in Denmark.
Harold Harefoot's short reign was the working-out of Cnut's untidy inheritance. Cnut's death in 1035 left two sons by two mothers: Harthacnut, the designated heir, pinned in Denmark by the threat of Magnus of Norway; and Harold, on the spot in England with his mother Ælfgifu of Northampton and the backing of Earl Leofric and the fleet.
Chosen first as regent at the Oxford assembly of 1035, Harold was full king by 1037. His reign's darkest act was the seizure and blinding of the ætheling Alfred, Æthelred's son, in 1036 — a crime that shadowed Earl Godwin, his agent in it, for the rest of his career.
Harold was born around 1016 to Ælfgifu of Northampton, Cnut's first, "handfast" wife, whose midland family had been mauled by Æthelred's regime. His nickname, first recorded later, was taken to refer to speed in the hunt.
While Emma of Normandy's son Harthacnut was groomed for Denmark, Harold and his brother Sweyn were deployed by Cnut through their mother — Sweyn and Ælfgifu ruling Norway in the early 1030s so harshly that the Norwegians rose and expelled them, an experience of his mother's regency style that Harold presumably remembered.
Harold had the misfortune to be remembered chiefly by his enemies. The Encomium Emmae Reginae, written for his rival's mother, paints him as an impious usurper who shunned church services; the C manuscript of the Anglo-Saxon Chronicle doubted he was Cnut's son at all. These are the standard weapons of eleventh-century faction, not description.
His actions read differently: he outmanoeuvred Queen Emma, Earl Godwin, and the designated heir from a standing start, converted a regency into a crowned kingship within two years, and held England quiet enough that the sources record almost no internal disturbance. That suggests political competence of a high order in a very young man — exercised, in the Alfred affair, with the ruthlessness the age expected.
The Oxford meeting of 1035 split the realm functionally: Harold held the north and the machinery of government as regent, while Emma sat at Winchester keeping Wessex — and the treasury — for the absent Harthacnut. By 1037, with Harthacnut still detained, "Harold was everywhere chosen king", as the Chronicle puts it, and Emma was driven into exile at Bruges.
The turning point was the affair of the æthelings in 1036. Alfred, the younger of Æthelred's exiled sons in Normandy, crossed to England — to visit his mother, said his partisans; to bid for the crown, evidently feared the regime. Intercepted by Earl Godwin at Guildford, his companions were killed or mutilated and Alfred was blinded so brutally that he died at Ely. The deed secured Harold's throne and became the enduring stain on everyone associated with it.
Harold died at Oxford on 17 March 1040, aged about twenty-four, just as Harthacnut and Emma had assembled an invasion fleet at Bruges. England thus changed kings without a battle: the fleet sailed in peacefully at midsummer.
Harthacnut's first recorded act was to have his half-brother's body dragged out of its Westminster grave, beheaded by some accounts, and thrown into the marshes — recovered later, tradition says, by London fishermen and reburied in the Danish church of St Clement Danes.
Harold's five years demonstrated how completely Cnut's Anglo-Danish state ran on the earls and the fleet rather than on designated heirs: possession of England, not testamentary right, made the king. The lesson was not lost on the men of 1066.
The Alfred affair had the longer echo. It gave Edward the Confessor a lifelong grievance against Godwin's house, and Norman propaganda a ready-made atrocity with which to blacken Harold Godwinson's family a generation later.