Henry II (1154-89) was king of England, and the first ruler from The House of Plantagenet. He emerged from the chaos of the "Anarchy", the civil war between his mother Matilda and her cousin Stephen who usurped the crown against the wishes of his uncle Henry I. He married Eleanor Of Aquitaine who bore him five sons, but only the future Richard the Lionheart and King John of England outlived Henry. He grew up in exile in Aquitaine so he spoke virtually no English.
Famous today for three things:
1. Founded the concept of The Common Law, a legal system where the law is usually determined by court decisions, and the foundation for the legal systems of the UK, the United States and Commonwealth countries such as Canada.
2. After a dispute over who should be the High King of Ireland, he took advantage of a Papal Edict of 1158 - issued by the only English Pope, Adrian IV (born Nicholas Breakspeare (No, really)) - that gave overlordship of Ireland to the King of England to establish an English zone of control (The Pale) around Dublin, which had repercussions for centuries to come.
3. The most (in)famous thing was that he got into a savage argument with the original Turbulent Priest, his one time friend Thomas Becket, Archbishop of Canterbury, over whether the Church was subordinate to secular authority. His expression of frustration was construed to be a Royal Command: a Rhetorical Request Blunder. Four knights made haste to Canterbury and brutally murdered Becket. The murder of an archbishop at the altar of his own cathedral on orders from the King was considered the worst crime in Christianity for a long time, and clouded Henry's reputation in history. It was something Henry appeared to truly show regret and remorse for and he was publicly whipped as penance by the canons of Canterbury Cathedral. (Becket, on the other hand, got made into a saint and had a great film made about him in which he was played by Richard Burton).
England's most powerful time during the Middle Ages was during his reign. The lands under his control are known as the Angevin Empire. Not only did he rule pretty much all of Great Britain and Ireland, he also was in control of over half of France. For a while, it looked like England would become the dominant power in Western Europe, but his successors weren't as good at ruling as he was and things started to fall apart. This would eventually lead to The Hundred Years War. Modern scholars often say that Henry II was the first monarch responsible for a unified Britain.
When his wife Eleanor Of Aquitaine had had enough of his infidelity, she manipulated her surviving sons into rebellion against him (known as the Great Revolt), which was successful. Henry died believing his reign had been a failure. Today, he is remembered as England's greatest Medieval king.
He ended at #90 in 100 Greatest Britons.