On Christmas Day 1251, when he was ten, he was knighted at York by Henry III, and the following day he was married to the English monarch's eldest daughter, Princess Margaret.
Alexander proved a strong-willed king who, despite the English influence in his youth, refused to swear homage for his kingdom. He continued his father's efforts to establish Scottish mastery of the Isles.
In 1263 his army inflicted a notable defeat on Hakon, King of Norway, at the Battle of Largs in Ayrshire. The Norwegians were subsequently forced to concede to him the Western Isles and the Isle of Man, under the treaty of Perth in 1266.
Alexander established good relations with his brother-in-law Edward I. On 19 August 1274, Alexander and Margaret attended the coronation of her brother in Westminster Abbey. Margaret died six months later, leaving three children.
Within a few years, Alexander suffered a further series of family tragedies. His younger son David died in 1281 at the age of eight; his daughter Margaret, who had married King Eric of Norway, died in childbirth in 1283; and his elder son Alexander died childless in 1284 after a long illness.
A week after the prince's death, the Scottish Parliament recognised Margaret, the little daughter of Eric and Margaret, as the heir presumptive to the Scottish throne.
Alexander was only 44, and so he decided that the best way to avoid a constitutional crisis was to remarry and have more sons. On 14 October 1285 he therefore took as his wife Yolande, Comtesse de Montfort, daughter of Robert IV, Comte de Dreux.
Five months later, on 19 March 1286, Alexander's horse stumbled and he fell from a cliff near Kinghorn, Fife. The king was killed, leaving the Scots to mourn an energetic, effective monarch who had brought them peace and prosperity.
Image: Alexander III sits at the right hand of his brother-in-law, Edward I of England. The Royal Arms of Scotland can be seen above Alexander's head.