William III of England (c.1137 - 1159) was King of England (1154 - 1159), Count of Boulogne (1153 - 1159) and Earl of Surrey jure uxoris (1153 - 1159).
Little is known of William's early life until his marriage with Isabel de Warrenne, 4th Countess of Surrey in 1148, when he was probably only 11 years old. This union and many land grants from his father, primarily in East Anglia, made young William very rich indeed and fate contrived to make him king after the early death of his elder brother, Eustace, in 1153 and their father, Stephen of Blois, the next year.
When he succeeded to the throne he was approximately 17 years of age and was therefore under the regency of his cousin, Henry I of Champagne (later Henry II) for the next four years, as 21 was the age of majority in those days. During this time the state of the realm was parlous. Nineteen years of civil war had desolated and impoverished the land and his frankly idiotic father had given away most of the crown lands of England, reducing royal revenue and increasing the arbitrary power of the magnates. This situation was gradually improved during the regency, as Henry of Champagne revised the law codes with the help of William's uncle, Bishop Henry of Winchester. This, among other things, established the 'King's Peace' which was the first effective feudal judiciary after the Norman Conquest. Furthermore, in 1157, a Court was convened to settle property disputes fairly - though this was inevitably a rather crude system as charter could be forged and even when they were not, they could be mutually contradictory.
Norman-Angevin War and Death
The greatest crisis of William's short reign came when, in 1158 (the year of his majority), Normandy was invaded by Geoffrey, Count of Anjou, a younger brother of Henry FitzEmpress, who had been murdered in 1152 while in pursuit of an unwilling wife. Count Geoffrey ravaged the land around Argentan for several months before an army of Anglo-Norman nobles could assemble, but the Battle of Falaise was a crushing victory for William, who was growing up to be an adequate king, though distressingly pious as a result of the influence of his ecclesiastical uncle. Unfortunately for the Church, William III died in 1159, at the age of 22.
William's barely expected death threw the fragile Anglo-Norman state into disarray. The main reason for having the House of Blois on the throne was that they could supply strong rulers as opposed to the women and children descended from Henry I. But William III acceding as a minor had shaken the chauvinistic nobles and now it looked like he would be succeeded by his sister Marie, who was a nun. With unseemly haste, therefore, Henry of Champagne seized the throne, basing his claim on his previous experience as Regent and being the son of an elder brother of Stephen, thus having a slightly better claim than the last pair of kings (though the brothers did have a still older brother who was probably mentally retarded). He was quickly enthroned.