The youngest and most able of William the Conqueror's sons, Henry strengthened the crown's executive powers and modernised royal administration.
Henry was born in England in 1068 or 1069, the fourth son of William the Conqueror. By the time his elder brother William became king, one of Henry's other older brothers had died, leaving Robert as the only other potential successor. William was killed in a hunting accident in August 1100, and Henry had himself crowned a few days later, taking advantage of Robert's absence on crusade. With a number of barons supporting Robert, however, Henry's succession was precarious. He moved quickly to buy support by granting favours, abolishing abuses and making wide-ranging concessions in his Charter of Liberties. In November 1100, he married Edith, sister of the king of Scotland, in order to secure his northern border.
When Robert invaded England in 1101 Henry, with some popular and baronial support, agreed an amicable settlement. Robert relinquished his claim in return for Henry's territories in Normandy and a large annuity. But his chaotic reign of Normandy prompted Henry to invade. He routed Robert's army at Tinchebrai in 1106, capturing Robert and holding him prisoner for life.
Henry's frequent absences from England prompted the development of a bureaucracy that could operate effectively in his absence. His reign marked a significant advance from personal monarchy towards the bureaucratised state of the future. The exchequer was developed to deal with royal revenues and royal justices began to tour the shires to reinforce local administration and inquire into revenues, often aggressively.
Abroad, his possessions in Normandy were challenged by Robert's son, William Clito. Henry was obliged to repel two assaults by Clito's supporters and Norman barons who resented Henry's officials and high taxes. By 1120, however, the barons had submitted, Henry's only legitimate son William had been married to the daughter of the powerful Count of Anjou and Louis VI of France had agreed terms for peace after defeat in battle.
In November 1120, Henry's son died in a shipwreck and from them on the question of the succession dominated the politics of the reign. Henry summoned his only other legitimate child Matilda, back to England and made his barons pay homage to her as his heir. In 1128, Matilda was married to Geoffrey Plantagenet, another member of the Angevin family. English barons did not want to be ruled by a woman and an Angevin and on Henry's death in December 1135, there was a succession crisis which led to civil war.