Gherbod was the very first Earl of Chester after the conquest. He is also the father of Gundred, wife of William de Warenne, 1st Earl of Surrey. Allegedly the mother was William the Conqueror's wife, Matilda of Flanders, who married or had an affair with Gherbod, before she m. William I. For a long time genealogists thought Gundred was a daughter of William I.
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EARLDOM of CHESTER (I)
Gherbod, a Fleming, Avoue of the Abbey of St. Bertin, received, on the dismemberment of Mercia, early in 1070, a large portion of that district, together with the city of Chester, the said portion being formed into a County Palatine (under the name of Cheshire) whereby he became Earl of Chester. He returned shortly afterwards, to his native country, where he was taken prisoner at the battle of Cassel, 1071, and kept captive for a long period, never coming back to England. [Complete Peerage III:164]