Robert Earl of Gloucester, natural son of the late King, came into England some time after the advancement of Stephen to the crown; and, yielding to the necessity of the time, took the oath of fealty upon the same condition used by the other nobles, to be of force so long as the King should keep his faith with him, and preserve his dignity inviolate:  but, being in his heart wholly devoted to the interests of the Empress his sister, and moved by the persuasions of several religious men, he had, with great secrecy and application, so far practised upon the levity or discontents of several lords, as to gain them to his party:  for the King had, of late, very much alienated the nobles against him; first, by seizing several of their persons, and dispossessing them of their lands; and, secondly, by taking into his favour William d’Ypres, a Flemish commander, of noble birth, but banished by his prince.  This man, with many of his followers, the King employed chiefly both in his councils and his armies, and made him Earl of Kent, to the great envy and displeasure of his English subjects.  The Earl of Gloucester, therefore, and his accomplices, having prepared all things necessary for an insurrection, it was agreed among them, that while the King was engaged against the Scots, each of them should secure what towns and castles they could, and openly declare for the Empress.  Accordingly Earl Robert suddenly fortified himself in Bristol; the rest followed his example; Hereford, Shrewsbury, Ludlow, Dover,[30] and many other places, were seized by several lords, and the defection grew so formidable, that the King, to his great grief, was forced to leave his Scottish expedition unfinished, and return with all possible speed to suppress the rebellion begun by his subjects; having first left the care of the north to Thurstan Archbishop of York; with orders carefully to observe the motions of the Scots.

[Footnote 30:  Robert Earl of Gloucester had been entrusted by Stephen with the custody of Dover Castle:  but Robert lying now under heavy suspicion, the King sent Matilda his queen to besiege it, in which she was successful. [D.S.]]

Whilst the King was employed in the south in reducing his discontented lords, and their castles, to his obedience, David, presuming upon the distance between them, reentered England with more numerous forces, and greater designs, than before:  for, without losing more time than what was necessary to pillage and destroy the country as he marched, he resolved to besiege York, which, if he could force to surrender, would serve as a convenient frontier against the English.  To this end, advancing near the city, and having pitched his tents, he sat down before it with his whole army.  In the mean time Archbishop Thurstan, having already summoned the nobles and gentry of the shire and parts adjacent, had, by powerful persuasions incited them to defend their country against a treacherous, bloody, and restless enemy:  so that before the King of