Sinking of the White Ship in 1120 off Barlfleur on the Normandy coast drowned William Adelin, only legitimate son of Henry I, and brought 20 years of civil war to England between Maud (Matilda), daughter of the king, and Stephen of Blois, the King's nephew. The period was known as The Anarchy (1135-1153), resolved by the accession to the throne of Maud's son by Count Geoffrey of Anjou: Henry II, the first Plantagenet.
Also on these boards
King Henry II : King of England 1154–89. The son of Matilda and Geoffrey V, Count of Anjou, he succeeded King Stephen. He curbed the power of the barons, but his attempt to bring the church courts under control was abandoned after the murder of Thomas à Becket. The English conquest of Ireland began during Henry's reign. On several occasions his sons rebelled, notably 1173–74. Henry was succeeded by his son Richard (I) the Lionheart.
King Harthacnut: eldest son of King Canute II and Emma of Normandy, heir to the English crown. He had been proclaimed king of Denmark in 1028 but when Canute died he was defending his land in Denmark. In his absence his illegitimate half-brother, Harold Harefoot was crowned King Harold I of England in 1037. Naturally there was a struggle between the two brothers that only ended on the death of Harold. Harthacnut sailed to England with a large fleet and was immediately accepted as king.
Stephen the Usurper! He was the nephew of Henry I, who had named his daughter, the Empress Matilda, as his heir after his only legitimate son died in the White Ship disaster. Because it was unheard of for a woman to rule England, members of the nobility who had pledged allegiance to Matilda while Henry was alive abruptly ditched her for Stephen after Henry I's death. A civil war that lasted years was the result. Stephen managed to hang onto the throne, fighting Matilda's faction to secure the throne for his son, Eustace. But Eustace died young, and Stephen saw the writing on the wall. He and Matilda called a truce -- Stephen would remain king until he died, but the throne would then pass to Matilda's son, Henry, who became Henry II.