Agnes of Essex, Countess of Oxford (1151– 1212 or later) was the daughter of a royal constable Henry of Essex and his first wife, Cecily.[1][2] At the age of three she was betrothed to Geoffrey de Vere, brother of the first Earl of Oxford, and turned over to be raised by the Veres soon thereafter. She remained in the household of the earl of Oxford about three years, then moved to Geoffrey's care. In her eleventh year Agnes rejected the match with Geoffrey and by early 1163 was married to his eldest brother Aubrey de Vere III, 1st Earl of Oxford, as his third wife.
In spring 1163, Agnes's father Henry was accused of treason and fought (and lost, although he survived and retired to a monastery) a judicial duel. After her father's disgrace and the resulting forfeiture of his lands and offices, the earl of Oxford sought to have his marriage to Agnes annulled. On 9 May 1166, she appealed her case from the court of the bishop of London to the pope (the archbishop of Canterbury, Thomas Becket, being in exile at the time).[3] While the case was pending in Rome, the earl reportedly kept Agnes confined in one of his three castles, for which the bishop of London Gilbert Foliot reprimanded Aubrey.[3] Pope Alexander III ruled in her favor, thus establishing the canon law requirement of consent by females in betrothal and the sacrament of marriage.
The couple later jointly founded a Benedictine priory for nuns near their castle at Castle Hedingham, Essex around 1190. Countess Agnes long survived her husband and in 1198 paid the crown for the right to remain unmarried. She died sometime in or after 1212 and was buried in the Vere mausoleum at Colne Priory, Essex.[4]