Harthacnut was born shortly after the marriage of his parents in July or August 1017. Cnut had put aside his first wife Ælfgifu of Northampton to marry Emma, and according to the "Encomium Emmae Reginae", a book she inspired many years later, Cnut agreed that any sons of their marriage should take precedence over the sons of his first marriage. In 1023, Emma and Harthacnut played a leading role in the translation of the body of the martyr St Ælfheah from London to Canterbury, an occasion seen by Harthacnut's biographer, Ian Howard, as recognition of his position as Cnut's heir in England.