Henry III (1 October 1207–16 November 1272) became King of England in 1216 when he was 9 years old, after the early death of his father King John. He would end up ruling as king for 56 years (though he would only effectively rule for around 45 due to his youth in the first years). He would be married to Eleanor of Provence, who bore him 5 children, for 36 years. During his long reign, Henry's kingdom would experience relative peace and prosperity until he began having trouble with his barons (particularly Simon de Montfort) due to his high handed governing style, which compelled the Barons to impose the Provisions of Oxford limiting royal power in 1258. 