Becoming Earl of Mercia, which occurred at some date previous to 1032, made him one of the most powerful men in the land, second only to the ambitious Earl Godwin of Wessex, among the mighty earls. Leofric may have had some connection by marriage to Ælfgifu of Northampton, the first wife of Cnut, which might help to explain why he was the chief supporter of her son Harold Harefoot against Harthacnut, Cnut's son by Emma of Normandy, when Cnut died in 1035. However, Harold died in 1040 and was succeeded by his brother Harthacnut, who made himself unpopular by implementing heavy taxation during his short reign. Two of his tax-collectors were killed at Worcester by angry locals. The king was so enraged by this that in 1041 he ordered Leofric and his other earls to plunder and burn the city, and lay waste to the surrounding area. This command must have sorely tested Leofric, since Worcester was the cathedral city of the Hwicce, his people.