Agnes of Essex, Countess of Oxford
Agnes of Essex, Countess of Oxford (c. 1151 – c. 1212) was the daughter of a royal constable Henry of Essex and his second wife, Alice de Montfort. She was betrothed at age three to Geoffrey de Vere, brother of the first Earl of Oxford, and turned over to be raised by the Veres soon thereafter. Agnes later rejected the match with Geoffrey and by 1163 was married to his eldest brother Aubrey de Vere III, 1st Earl of Oxford, as his third wife.
In 1163, Agnes's father was accused of treason and lost a judicial duel. After her father's disgrace and the resulting forfeiture of lands and offices, the earl sought to have his marriage annulled. Agnes fought his action. 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). 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. Pope Alexander III ruled in her favor, thus establishing the canon law right and requirement of consent by females in betrothal and the sacrament of marriage.
The couple seem to have jointly founded a Benedictine priory for nuns near their castle at Castle Hedingham, Essex. Countess Agnes 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.
Many mistakenly have called Earl Aubrey's third wife Lucia, rather than Agnes. This mistake is based on a misreading of a single document associated with a religious house at Hedingham, Essex, established around 1190. A woman named Lucia was prioress at Castle Hedingham Priory. On her death in the early thirteenth century, an illustrated mortuary or 'bede' roll was carried to many religious houses requesting prayers for her soul. In the preface of that document Lucia is called the foundress of the priory. As the role of "founder" is generally ascribed to lay patrons and the countess presumably cooperated with her husband in the founding of the house, the erroneous assumption was made that the prioress was Earl Aubrey's widow, rather than Agnes, by 18th-century scholars. That is disproved by royal records. 
Agnes bore her husband four sons and a daughter, including two future earls of Oxford: Aubrey IV and Robert I. Her daughter Alice married 1) Ernulf de Kemesech, 2) John, constable of Chester. Agnes's son Henry appears to have become chancellor of Hereford Cathedral under his uncle, Bishop William de Vere, and later a royal clerk under King John of England. Little is known of Roger de Vere except that he seems to have been the second son and that he had died by 1214, when his younger brother Robert succeeded to the earldom on the death of the eldest son Aubrey IV, 2nd earl, in 1214.
- R. DeAragon, "The Child-Bride, the Pope, and the Earl: The Marital Fortunes of Agnes of Essex," Henry I and the Anglo-Norman World (Woodbridge: 2004), 201.
- The Letters and Charters of Gilbert Foliot, ed. Morey & C. N. L. Brooke (Cambridge University Press, Cambridge: 1967) #162, pp. 214-218.
- G. E. Cokayne, The Complete Peerage of England...., v. 10, p 207.
- RaGena DeAragon. "The Child-Bride, the Earl, and the Pope: The Marital Fortunes of Agnes of Essex", Henry I and the Anglo-Norman World (2007), Boydell & Brewer.
- G. E. Cokayne, Complete Peerage, vol. 10, 208