From "Debrett's Kings and Queens of Britain" by David Williamson, ISBN 0-86350-101-X, p. 43-6:
Acceded to the throne of England by conquest 14 Oct 1066. Crowned at Westminster Abbey 25 Dec 1066
The illegitimate son of Duke Robert 'the Devil' or 'the Magnificent.' The taint of bastardy mattered very little where the ducal succession was concerned and it can hardly have had any psychological effect on William, since most of his ancestors in the Ducal line were also bastards.
William was only 7 or 8 when he succeeded to the duchy on the death of his father in 1035. William grew up under the protection of Alan, Count of Brittany, Gilbert, Count of Brionne, and Osborn the Seneschal. All three fell victim to an assassin. When William was still under 20 he defeated an attempt to wrest the duchy from his control by his cousin, Count Guy of Burgundy, and a faction of dissatisfied nobles.
In 1053 William made an advantageous marriage with Matilda, the daughter of his neighbor, Count Baldwin of Flanders. There was some ecclesiastical objection to the marriage which has never been satisfactorily unravelled and it was not until 1059 that the Pope gave his approval. The couple expiated their 'sin' by founding two abbeys - the Abbaye-aux-Hommes (St Stephen's) and the Abbaye-aux-Dames (Holy Trinity) - at Caen. William and Matilda became devoted to each other and, in an age when marital infidelity was the norm, we hear of no mistresses. William's marriage may well have been partly motivated by his growing ambition to gain the throne of England, for Matilda was a direct descendant of Alfred the Great.
William had visited his first cousin once removed, Edward the Confessor, in 1051, when he had been well received and designated as Edward's successor. In 1064 fortune played into his hands when Harold, Earl of Wessex, was driven ashore on the coast of Ponthieu. He was received with great honor, but before sending him home, William extracted an oath from him to uphold his claim to the English throne on the death of Edward.
Edward died and Harold was crowned King in Jan 1066. William at once began careful preparations for an invasion. He was not hurried and, when he was ready to set sail in the late summer, was delayed further by an adverse wind. Harold, meanwhile, was forced to march north to deal with the Norwegian invasion and while he was away the wind changed and William landed with his troops at Pevensey on 28 Sep. He stumbled on leaping ashore, but allayed the fears of those of his supporters who saw this as an ill omen by holding aloft a handful of sand and shouting that he had already taken possession of his kingdom. William bided his time at Hastings and began constructing a castle there while waiting for Harold to arrive from the north. He may have thought that Harold would surrender easily, exhausted by his action against the Norwegians and his march south, but the battle, when it took place on 14 Oct, was hard fought, and after a full day's fighting ended with Harold's death. William marched to London with his victorious army, laying the land waste around the city until local resistance collapsed and the English nobles led by Edgar Atheling [the rightful heir to the throne] submitted to the Conqueror.
On Christmas Day 1066 William was crowned at Westminster Abbey by Aldred, Archbishop of York. The shouts of acclamation - in English as well as in French - from the congregation inside the Abbey alarmed the Norman guards stationed outside. Mistaking the noise for signs of an insurrection, they began a massacre of the Saxons living nearby, burning and pillaging their houses and the King himself appeared at the doorway of the Abbey to quell the tumult.
Although the south and east of England quickly submitted to William's rule, over the next five years there were risings in various parts of the country. The south-west submitted in 1068 and the rebellion in the north of the Earls Edwin and Morcar was put down in person by William in 1069, and was followed by the 'harrowing of the north' a laying waste from York to Durham. A rising in the Isle of Ely led by Hereward the Wake was put down in 1071. During this period the Normans had to live like an army of occupation, building castles from which a few men could dominate the subject population.
Gradually during William's reign English lords were superseded by Norman and other French barons and the Continental system of feudal land tenure was introduced. In the Church, too, English bishops were replaced by Continental prelates and Lanfranc of Pavia, who was appointed Archbishop of Canterbury, reorganized the English Church on European lines. The Domesday Survey, commanded in 1086, gave the King, as chief lord of this feudal system, an exact account of his power and resources for administrative purposes.
After 1071 William felt secure enough in England to turn again to his Continental possessions which were more vulnerable to attack than his island kingdom. His borders were continually threatened by his neighbors, the King of France and the Count of Anjou, who enlisted the support of William's disaffected eldest son Robert. The rest of William's reign was taken up with a series of intrigues by these enemies.
The French King's facetious remarks about William's excessive corpulence prompted him to threaten to 'set all France ablaze.' In 1087 the French garrison at Mantes made a raid into Normandy and William retaliated by sacking Mantes. As he was urging on his men his horse stumbled on a hot cinder and he was flung violently against the high pommel of the saddle. He sustained grave internal injuries, probably a ruptured bladder, from which peritonitis ensued, and he died after much suffering on 8 Sep 1087.
His burial in his foundation of St Stephen at Caen was fraught with incident. As the cortege neared the church a citizen barred the way, claiming that it had been built on land illegally seized from his family, and was only appeased by an on the spot payment of cash. On reaching the grave it was found that it had been made too small and the bearers, in attempting to force the fast decomposing corpse into it, burst it open so that a vile stench filled the church, causing all but the hardiest to flee, and the burial was completed by a handful of faithful retainers.
The writer of the Anglo-Saxon Chronicle, who knew William and at one time lived in his court, summed him up as 'a man of great wisdom and power, and surpassed in honor and in strength all those who had gone before him. Though stern beyond measure to those who opposed his will, he was kind to those good men who loved God . . . He wore his royal crown three times a year as often as he was in England; at Easter at Winchester, at Whitsuntide at Westminster, at Christmas at Gloucester. On these occasions all the great men of England were assembled about him.' He was grasping and mendacious but a great ruler and far in advance of his times as a legislator. William, who was about 60 at the time of his death, was a tall man of ruddy complexion, always inclined to corpulence, and for most of his life probably clean shaven. The only contemporary likenesses of him are in the Bayeux Tapestry.

Reigned 1066-1087. Duke of Normandy 1035-1087. Invaded England defeated and killed his rival Harold at the Battle of Hastings and became King. The Norman conquest of England was completed by 1072 aided by the establishment of feudalism under which his followers were granted land in return for pledges of service and loyalty. As King William was noted for his efficient if harsh
rule. His administration relied upon Norman and other foreign personnel, especially Lanfranc Archbishop of Canterbury. In 1085 started Domesday Book.

William the Conqueror gave England a form of government quite different from that of most other lands. France was ruled by a king; but France had many dukes who controlled whole provinces that were virtually kingdoms within the kingdom. William had been just such a mighty duke in France, and he wanted no local rulers of this sort to plague him now that he had won a country of his own. He took good care to scatter the estates of his earls and barons, giving them strips of territory here and there but not letting any of them gain power over a single great domain. The king was supreme.119