Mabel, heiress of Oval and through her mother of the St. John honour of Halnaker. [Origins of Some Anglo-Norman Families]
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Adam [de Port] married, 1stly, Mabel, heiress of Orval and thereafter through her mother of the St John honor of Halnaker (f). [Complete Peerage]
(f) Adam's son and heir, styling himself "Willelmus de Sancto Johanne secundus," executed a charter for Boxgrove Priory "pro animabus Willelmi et Roberti de Sancto Johanne et Ade de Port patris mei et Mabilie matris mee". According to the "Fundationis", Mabel was daughter of Rainald d'Orval by Muriel, daughter of Roger and sister of William and Robert de St. John. Round accepted this provisionally on the ground that the "Historia" was obviously more trustworthy than such narratives usually are. That Mabel was the heiress of Orval is certain, since a gift of William d'Orval to the abbey of Blanchelande was subsequently confirmed by Adam de Port and Mabel his wife as the gift of their predecessor. It is equally certain that Halnaker came to Port through Mabel and her mother, and this being so the mother must have been a daughter of Roger and a sister of William and Robert de St. John, not only on chronological grounds but also because, if she had been of an earlier generation, Roger's brother John de St. John and his male issue would have inherited to her exclusion. Since the wife of Robert de la Haie was named Muriel and they were the parents of Cecily, Roger de St. John's wife, it is quite likely that Roger's daughter should have been named after her, and on this point one seems justified in accepting the statement of the "Historia." The real difficulty lies in the name of Mabel's father. The only Rainald d'Orval who so far as can be seen was seigneur of Orval witnessed a charter of Robert Curthose between 1101 and 1105 made gifts to Lessay recorded in a later notification. The full text of the latter shows Rainald to have had a son Hugh who succeeded him and who was in turn succeeded by his son William, which last was in possession before 1151, since a gift of his to Lessay was confirmed by Geoffrey, Duke of Normandy and Count of Anjou. This William had a son Richard, who, with his father, witnessed a charter of William and Robert de St. John for La Luzerne in 1162. William d'Orval seems to have died at some date before Michaelmas 1179, since his lands were in the King's hand from then to the end of the year. As the lands then passed to Adam de Port and his wife, Richard must have predeceased his father. A Rainald d'Orval renders account at the Norman Exchequer at Michaelmas 1180, but in the "prepositurs" of Nonancourt; and since Orval had by that time passed to Mabel and her husband he could not have been her father. To sum up; it is difficult to see how Mabel's father could have been a Rainald d'Orval and his name must remain uncertain; but the suggestion may be hazarded that she may have been the daughter of Richard, son of William d'Orval and that the "Reginaldus" of the "Historia" may be a scribal error for "Ricardus".