 William made one final attempt to take the county in 1130, though the events are veiled in obscurity.He was unable to prevail against Thierry and unlike his predecessors, Thierry was less than forgiving, banishing William from Flanders sometime between 1133 and 1135..

Having failed to established himself as Count of Flanders, William went from his wife's lands in Sluis to Stephen's County of Boulogne.Stephen's accession to the English throne following Henry I's death in 1135 finally changed William's fortunes for the better.