Guillaume de Grandmesnil (de Grentmesnil), Heir of the honour of Grandmesnil - Wiiiam 1 de Grandmesnil

From FMG:

"He took part in Robert Guiscard's campaign against Durazzo in 1081 and was summoned by Duke Robert to his deathbed. He was granted land in the valleys of the Crati, the Coscile and at Cotrone, although it is not known whether this refers to part of the "15 castles" of his wife's dowry...or whether they were grants made to Guillaume in his own right before his marriage. Either way, it is clear that Guillaume's career in Apulia must have been particularly successful for him to have risen from a relatively obscure background and to have made such a prominent marriage. Orderic Vitalis reports that in [Jul] 1097 Guillaume and his brother Aubrey were among those who, fearing that Antioch would be recaptured by the Turks, let "themselves down the wall with ropes" in order to escape and "were called clandestine rope-dancers to their lasting disgrace". Albert of Aix records "Guillaume", married to the sister of Bohémond, and formerly domestikos of the Emperor at Constantinople, who escaped "out of fear" from Antioch to Alexandretta, believing that the crusading army was doomed after it was besieged by Kerbogha atabeg of Mosul. He died in Apulia after returning from Antioch according to Orderic Vitalis, the text suggesting that this was before 1114."

Other research showed William was disgraced in England and returned to the Levant and was given a small Lordship by the Byzantine emperor. It is said he died in an earthquake.