uncle, King Henry I of England [q. v.], who therefore sent to Flanders another of his nephews, Stephen [see Stephen, King of England], to form a league with the nobles against Clito. This league was joined by William of Ypres. As early as 24 March, indeed, it had been reported at Bruges that King Henry had furnished William with three hundred knights and ‘no end of money’ to help him in mastering Flanders; but the truth seems to be that William had received from Bertulf's family five hundred pounds in English coin, stolen from the late count's treasury, and he represented this as a gift from the English king in order to conceal his dealings with the traitors. On 9 April Louis met William at Winendale, and endeavoured to bring him to agreement with Clito; ‘but the unlawful count disdained to agree with the true count, or to make any terms of peace with him, for he despised him.’ Next day William learned that Bertulf was hidden near St. Omer in the house of one Alard. He first vainly searched and then burned the house of Alard and that of his daughter, and carried the daughter off to Ypres, threatening to mutilate her and seize all Alard's possessions unless Bertulf were given up to him on the morrow. Next morning Alard sent Bertulf in custody to Ypres. William was just going to preside at the trial of one of Bertulf's accomplices, Guy of Steenword. Guy and Bertulf were hanged the same day in William's presence. Bertulf's last words were an insinuation that William had been privy to the plot for which he sent them to the gallows. On 26 April Louis and Clito attacked Ypres. William marched out with three hundred knights to meet them; after a three hours' fight, the citizens, according to a secret agreement which they had made with Louis, opened one of their gates to the French; William fled, but was overtaken, captured, and imprisoned, first at Lille, then at Bruges, and then at Lille again. In spring 1128 Clito was expelled from Bruges and Ghent by a new rival, Thierry of Alsace; and in March he released William and proposed that they should make common cause against Thierry. On 27 July Clito fell in battle; and on 22 Aug. a charter of Thierry, count of Flanders, was witnessed by ‘William of Loo’ (Duchesne, Hist. de Guines, preuves, p. 209). In 1130 ‘William, son of Count Philip,’ witnessed a grant made to the monastery at Loo by Thierry and his wife Swanhild. William and Swanhild were somehow akin (possibly half-brother and sister); ‘many evils befell through Swanhild's kinsfolk,’ and William ‘was secretly of her party, because of their relationship.’ After her death, which occurred in 1130, he was compelled to give up the castle of Sluys, which he had held for some time in defiance of Thierry. In 1133 Thierry drove him out of Flanders, and he took refuge in England, seemingly in the household of Stephen.
Stephen, on his accession to the crown (December 1135), engaged a force of Flemish mercenaries, set William at their head, and took him for his chief confidant, much to the disgust of the barons. In 1137 William accompanied the king to Normandy, and while there plotted with him to capture Robert, earl of Gloucester [q. v.] When Geoffrey of Anjou invaded the duchy in May, William endeavoured to intercept him at Le Gué-Béranger, but failed because the Normans would not act with him. In May 1138 he went to Normandy again with Count Waleran of Meulan, and they attempted to restore Stephen's authority there by force. In July they gathered a great host to meet another Angevin invasion, and when Geoffrey retired without fighting, they turned their arms against Earl Robert at Caen, but without success. When Stephen besieged Devizes in June 1139, he sent William before him with a threatening message to its garrison. At the battle of Lincoln on 2 Feb. 1141, William shared with the Count of Aumale the command of the second division of Stephen's forces, which, after repelling a flank attack of the empress's Welsh auxiliaries, was routed by her English troops. Like all the other leaders on Stephen's side, William fled; ‘being highly skilled in war, and seeing the impossibility of helping the king, he reserved his aid for a better opportunity.’ The king was made prisoner; William joined the queen in Kent, and helped her to raise fresh forces, with which in July they besieged the empress at Winchester. In September he and his Flemings surprised and captured two hundred of the empress's partisans near Wherwell Abbey (John of Hexham, p. 310, Rolls ed.) In the battle near Winchester on 14 Sept. he captured Humphrey de Bohun (d. 1187) [q. v.], and led the Flemings in pursuit of Robert of Gloucester till they surrounded and made him prisoner at Stockbridge. In November Robert was exchanged for Stephen, who therefore considered himself indebted to William for his liberation. Later Flemish historians assert that he rewarded his liberator with the earldom of Kent, and many English writers have accepted the statement, but it is incorrect. The contemporary ‘Genealogia Comitum Flandriæ’ says that ‘the king granted to his deliverer