=18. William's Invasion.=--In 1072 William came north with a fleet and an army to avenge Malcolm's raid. He went as far as _Abernethy_ on the _Tay_, the former Pictish capital, and there Malcolm met him and acknowledged William as over-lord, by becoming his man or vassal, giving hostages, among whom was his own son _Duncan_, as warrants for his good faith. But some years later Malcolm took advantage of William's absence in Normandy to harry his kingdom again as far as the _Tyne_, bringing back both spoil and captives. The Conqueror's eldest son, _Robert_, came north to avenge this invasion, but happily he and Malcolm came to terms without any more bloodshed. This peace was not broken till 1092, when Malcolm again invaded England. The excuse for this was that his brother-in-law, the Ætheling, had been turned out of the retreat in Normandy granted to him by the Conqueror. _William Rufus_, who now sat on his father's throne, marched into _Lothian_, where peace was again made by the mediation of Robert and Eadgar. Malcolm renewed his homage, and William renewed the grant made by his father of certain manors and a yearly payment of twelve marks. But William did not keep to the terms of the treaty, and when Malcolm complained of this breach of good faith he was summoned to appear before the English court at _Gloucester_. He went, but soon came away again, justly incensed at the insulting way in which he was treated by being put on the same level as the Norman barons. For the fifth time Malcolm entered England at the head of an army, but from this expedition there was no triumphant return, for the king and his son were slain on the banks of the _Alne_, and the host that had followed them fled in great confusion.