On 18 June 1066 Matilda of Flanders, the wife of William the Conqueror, was involved in the foundation of the abbey of La Trinité of Caen. Her activity was recorded in the abbey's foundation charter which gives the details of many grants made to the new abbey, and Matilda is described as acting in a variety of roles within it. Together with her husband William she made donations of land and gave her daughter Cecilia to the abbey as an oblate. She also independently donated her own land, purchased land on behalf of her foundation, interceded with others to influence them to donate, and made a counter-gift to one of the donors. Finally, Matilda subscribed the charter along with her husband and her three sons.

There is much of interest in this document, not least the different roles that Matilda plays, and the different ways that Matilda is described: as a daughter of the count of Flanders when she is founding the abbey; as a wife when she and William give their daughter Cecilia as an oblate; but most frequently as comitissa, or countess. Matilda is given the title when she acts as a donor, as an intercessor, as a counter-gifter, and as a subscriber, but the fact that the title comitissa is not consistently used at all times raises questions about the meaning of the description. Was the title an indication of a female office? Was a distinction made between the role of a wife and the role of a countess?