Walter Scott writes of William's travails at Alnwick in his "Tales of a Grandfather: History of Scotland":
...Now William, King of Scotland, having chosen for his armorial bearing a Red Lion, rampant (that is, standing on its hind legs, as if it were going to climb), he acquired the name of William the Lion. And this Rampant Lion still constitutes the arms of Scotland, and the President of the Heralds' Court in that country, who is always a person of high rank, is called Lord Lion King-at-Arms.
William, though a brave man, and though he had a lion for his emblem, was unfortunate in war. In the year 1174, he invaded England, for the purpose of demanding and compelling restoration of the portion of Northumberland which had been possessed by his ancestors. He himself, with a small body of men, lay in careless security near Alnwick, while his numerous, but barbarous and undisciplined army, were spread throughout the country, burning and destroying wherever they came. Some gallant Yorkshire barons marched to the aid of their neighbors of Northumberland. They assembled four hundred men-at-arms, and made a forced march of twenty-four miles from Newcastle towards Alnwick, without being discovered. On the morning a thick mist fell, — they became uncertain of their road, — and some proposed to turn back. " If you should all turn back," said one of their leaders, named Bernard de Baliol, " I will go forward alone." The others adopted the same resolution, and, concealed by the mist, they rode forward towards Alnwick. In their way they suddenly encountered the Scottish King, at the head of a small party of only sixty men. William so little expected a sudden attack of this nature, that at first he thought the body of cavalry which he saw advancing was a part of his own army. When he was undeceived, he had too much of the Hon about him to fear. " Now shall we see," he said, " which of us are good knights ;" and instantly charged the Yorkshire barons, with the handful of men who attended him. But sixty men-at-arms could make no impression on four hundred, and as the rest of William's army were too distant to give him assistance, he was, after defending himself with the utmost gallantry, unhorsed and made prisoner. The English immediately retreated with their royal captive, after this bold and successful adventure. They carried William to Newcastle, and from that town to Northampton, where he was conducted to the presence of Henry II., King of f England, with his legs tied under his horse's belly, as if he had been a common malefactor or felon.
This was a great abuse of the advantage which fortune had given to Henry, and was in fact more disgraceful to himself than to his prisoner. But the English King's subsequent conduct was equally harsh and ungenerous. He would not release his unfortunate captive until he had agreed to do homage to the King of England, not only for his English possessions, but also for Scotland, and all his other dominions. The Scottish Parliament were brought to acquiesce in this treaty ; and thus, in order to recover the liberty of their King, they sacrificed the independence of their country, which remained for a time subject to the English claim of paramount sovereignty. This dishonorable treaty was made on the 8th of December, 1174...