Henry III became King of England within days of his ninth birthday. His father, King John, had overseen a disastrous period in English history and the boy king inherited a country embroiled in a bitter, entrenched war with itself. With barons inviting a French prince to take the crown, the young Henry was forced to rely on others to maintain his position. As he grew into adulthood, Henry had to manage the transition to a personal rule, wrenching power from men who had held it almost unchecked for years. With a settled position at home, attention could turn to the recovery of lost territory abroad and the salvaging of Henry’s family reputation. All would not go according to plan. Failures abroad led to trouble back in England as restless barons became disillusioned. They found a figurehead in Simon de Montfort, a man who would transform himself from Henry’s favourite to a de facto king. Imprisoned and stripped of his power, Henry would again have to fight for his kingdom, now relying not on older mentors but on his immensely capable son. Henry was handed a monarchy in peril, a crown that was cracked and tarnished. He was given fifty-six years to mend the damage his father had done. It would spell over half a century of highs and lows in a country crying out for stability; the final measure of Henry’s achievement displayed in the crown that he left to his son, Edward I.