One night in December, when the ground was covered with snow, Matilda quitted the castle at midnight, attended by four knights, who, as well as herself, were clothed in white. The party passed through the lines of their enemies entirely unobserved, and crossed the Thames, which was frozen over. The adventurous daughter of Henry I. then pursued her way, sometimes on foot, sometimes on horseback, to Wallingford, where she joined the army of her son and the Earl of Gloucester. [Illustration: _From the Picture by Sir John Gilbert, R.A., P.R.W.S._ THE BATTLE OF THE STANDARD, A.D. 1138. BY PERMISSION FROM THE PAINTING IN THE CORPORATION ART GALLERY OF THE CITY OF LONDON.] After having taken Oxford Castle, Stephen encountered the forces of the Earl of Gloucester at Wilton, and was defeated, the king himself having a narrow escape of a second imprisonment. A desultory warfare ensued, which lasted during three years, without any important advantage to either side. Prince Henry remained during this time at Bristol Castle, in the company of his uncle, the Earl of Gloucester, and in 1147 returned to Normandy. Soon after his departure, Robert of Gloucester died of an illness resulting from alternate excesses and privations. Deprived of the aid of her half-brother, who had governed her affairs with undoubted ability, Matilda found her position become every day less secure. One by one her most faithful partisans fell away, stricken down by disease, or weary of the contest; and among those who died was the Earl of Hereford, one of the ablest and most powerful defenders of her cause. At length the ex-empress determined to pass over into Normandy, there to concert with her husband and her son fresh measures for renewing the struggle. Emboldened by her absence, Stephen made vigorous attempts to re-establish his power upon a firm basis; and for this purpose he endeavoured by stratagem, as well as by force, to obtain possession of various strongholds which had been seized and fortified by the barons. The efforts thus made to reduce these haughty chiefs to submission met with little success, and the king's own adherents were ill-disposed to support a policy which they foresaw might one day be extended to themselves. [Illustration: GREAT SEAL OF HENRY II.] On the death of Innocent II. (September 24, 1144), the office of Legate of the Holy See was transferred from the Bishop of Winchester to Theobald, Archbishop of Canterbury. The archbishop, having proceeded to the Council of Rheims in opposition to the royal command, was banished from the court.