Malcolm’s hopes were rudely checked by the events of 1066. William’s introduction of a highly centralized rule ensured that for the future Northumbria would not be left to fight her own battles unaided, or, at least, unavenged. Yet for a time Malcolm’s marriage to Margaret, sister of Eadgar the Aetheling, and the considerable immigration into Scotland of fugitive Englishmen, seemed to promise otherwise. Cumberland, it must be remembered, was at present a part of Scotland, having been granted by Eadmund I., after his conquest of it, as a fief to Malcolm I., and Carlisle was an excellent base of operations. In 1070 Malcolm, starting thence, made another savage raid into Northumberland. William thereupon proceeded northward next year, with a great army and a fleet, and penetrated to the Tay. Malcolm made a vague submission, but in 1079, during William’s absence in Normandy, he made a third raid, which was replied to by a counter raid under Prince Robert. A fortress was then constructed on the Tyne to defend southern Bernicia, called the ‘New Castle.’ The result was immediate. Malcolm made no further attack for twelve years, and was then checked by the garrison of Newcastle. He made some kind of submission, but Cumberland was conquered by a treacherous attack of William Rufus, and the English king’s insults drove him to madness. He once more invaded Northumberland, and near Alnwick was defeated and slain. For many years after the famous king’s death there were no Scottish invasions. Scotland was much troubled with civil war, and afterwards divided between two sons of Malcolm. It was not until 1124 that David I. reunited the country under his rule. For eleven years his relations with England were peaceful, but when Stephen of Blois usurped the English throne, the Scottish king invaded Northumberland, nominally to support his niece, the Empress Matilda, really, of course, to make his profit out of the situation. Northumberland and Durham readily submitted to him as the representative of Matilda, and Stephen, pressed by many difficulties, was glad to purchase his withdrawal by the retrocession of Carlisle, nominally to David’s son Henry, who also received Doncaster and the Earldom of Huntingdon. But the great English magnates were bitterly indignant, and in 1138 war again broke out.