In the histories of the 7th century the actions of kings are writ large in war and in peace. Women of the royal houses are much more shadowy figures. We see them as elements in the dynastic politics of marriage alliances but rarely as active players in their own rights; and we may find them as widows retired to a monastery. Eanflæd fits this general pattern, yet if we look closely at events surrounding her life we find some indications of how a queen could act and influence the politics of the realm.

The course of her life was set within the dynastic politics of Northumbria and the relationships between its two royal houses of Bernicia and Deira. Eanflæd was born in 626 the daughter of Edwin of Deira, then king of Northumbria, and his wife Æthelburgh of Kent. She was born during the night following Easter Sunday, immediately after a crisis in which an assassin had attempted to kill her father. Her mother, the daughter of the French Princess Bertha and King Æthelberht of Kent, was a practising Christian within a pagan court; and some weeks after the birth Eanflæd was baptised a Christian by Paulinus, her mother's chaplain. Bede notes that she was the first of the Northumbrian people to be baptised.

In 633, when she was seven years of age, Northumbria was invaded from the south and Edwin was killed. Æthelburh fled back to Kent to the protection of her father's people, taking with her Eanflæd and others of the royal household. But when, two years later, the Bernician prince Oswald, son of Edwin's former adversary King Æthelfrith, gained the Northumbrian throne, Æthelburgh feared that even in Kent the Deiran children would not be safe. She therefore sent them to France to the court of her kinsman King Dagobert. So Eanflæd grew up in exile.

Eanflæd was brought back to Northumbria in 642 or 643, at the age of seventeen or eighteen years, for a marriage with Oswiu who had succeeded his brother Oswald as king. At the beginning of Oswiu's reign, the unity of the Northumbrian kingdom was by no means assured and as a son of Æthelfrith, his acceptability in Deira could not be guaranteed, despite his mother's Deiran lineage. The marriage alliance, then, was one element of a strategy to consolidate his position; and it gave Eanflæd a power which she was able to exercise in 651. In the early stages of his reign, Oswiu did not govern Deira directly, but via a sub-king. Between 646 and 651 the Deiran Prince Oswine was the sub-king but, after failing in an armed rising against Oswiu, he went into hiding, was betrayed and then murdered at Oswiu's behest. Thereafter, prompted by Eanflæd, Oswiu endowed a monastery at Gilling, within Deiran territory, and appointed Trumhere, a relative of the murdered sub-king, as its abbot. Bede explains this as an act of atonement, with the monks praying daily for the redemption of the souls of both the kings. The action can also be understood within a more general, non-Christian morality of the era. By the act of murder, Oswiu incurred liability for a blood debt and Eanflæd, as a kinswoman of the murdered man, was entitled to extract a price for expiation of the debt. The endowment of the monastery was the the price she exacted.

In the politics of religion within the royal household, Eanflæd exercised influence. She followed the practices of the Roman strand of Christianity which was her upbringing, despite the fact that Oswiu and his court followed the Irish Christianity established by Oswald at Lindisfarne. She was an early patron of Wilfrid who as a youth presented himself at her court and who in 664 spoke on behalf of the Roman tradition at the great debate at Whitby. There was something of a pro-Roman party, with a distinct Deiran slant, within the Northumbrian state. Eanflæd and her step-son Alhfrith were very much at its centre.

In maintaining her position in this way, Eanflæd was perhaps influenced by the example of her mother and her maternal grandmother, both of whom had practiced Christianity within pagan courts. The two Christian traditions represented at court used two different ecclesiastical calendars. As a result, the King could be celebrating Easter while the Queen and her court were still observing lent. Bede presents this as one of the factors which led Oswiu to call the Synod at Whitby where he decided in favour of Roman Christianity.

As a widow, after Oswiu's death in 670, Eanflæd entered the monastery of Whitby under the aegis of her kinswoman Abbess Hild. In doing so, she joined her daughter Ælfflæd whom Oswiu had dedicated to monastic life from her infancy. Whitby developed as a house monastery of the Deiran royal family: Eanflæd and Ælfflæd succeeded Hild in the post of Abbess. And it was during Eanflæd's time at the monastery that the bones of her father King Edwin were recovered from the site of his death at Hatfield Chase and enshrined beside the altar in the monastery church.

The date and circumstances of Eanflæd's death are not known. Although the details known of her life are few, nevertheless they afford us some insight into her influence in the dynastic and religious politics of the state.