Excerpts from Books and Wikipedia
"Matilda daughter of Henry I of England, had spent four years betrothed to Henry V. At thirteen she was finally sent to Mainz, where she married the twenty-eight-year-old emperor in a ceremony of 'fitting splendour' . . . Six years later, catastrophe struck at home. Her brother, William, a year her junior and the heir to the English throne, got drunk with friends and ordered a ship put out to sea for all of them. . . . All of the young men on the ship but one drowned; . . . The seventeen-year-old William was Henry's only legitimate son, Matilda his only daughter. . . . Before Matilda could cross the Channel and claim her crown, the noblemen of England—resistant both to the notion of a queen and to the French influence that would undoubtedly accompany her--banded together and proclaimed Matilda’s cousin Stephen, grandson of William the Conqueror, as king of England. . . . In 1139, four years after Stephen’s election, Matilda invaded England with troops from Anjou and Normandy. . . . This was the beginning of the Anarchy, a fifteen-year civil war that destroyed villages, killed thousands, wrecked the English countryside, and brought its people to despair . . ." "This will mark a 19-year period of Government strife and Civil War between the supporters of Stephen and Matilda, and end with the crowning of Matilda's son, Henry II, and beginning the Plantagenet dynasty." [Wikipedia: Timeline of Middle Ages]