Henry III of England was born in 1207, the son of the infamous King John and Isabella of Angoulême. His youth was overshadowed by the failure of his father's reign, especially with the Magna Carta's signing in 1215 and John's subsequent death in 1216. Henry became king at just nine years old, with England deeply divided and facing external threats, notably from France.

Regents governed on Henry's behalf during his early years, primarily William Marshal, Earl of Pembroke. As Henry matured, however, he began to assert his authority. Unfortunately, he lacked the administrative prowess or military skill of some of his predecessors. While deeply pious and dedicated to justice, Henry was often indecisive and easily influenced by his favorites.

His reign was marked by a deep attachment to the continental possessions that the Angevin kings once held, particularly Normandy. Henry tried unsuccessfully to reclaim these territories. Moreover, his expensive and futile foreign endeavors, including aiding the Papal States, put a strain on the royal treasury.

The ambitious rebuilding of Westminster Abbey and the elevation of his younger brother, Richard of Cornwall, to the title of King of the Romans, further drained funds. Financial pressure, combined with favoritism, stirred discontent among the nobility. His relationship with Parliament was tense, with Henry frequently bypassing traditional feudal councils in favor of smaller, more manageable gatherings.

Henry's reign witnessed the Provisions of Oxford in 1258, a set of constitutional reforms that sought to limit royal power and establish a more regular form of parliamentary governance. Though initially accepting them, Henry later repudiated these provisions, leading to the Second Barons' War between the king and a group of rebel barons led by Simon de Montfort. The conflict culminated in the Battle of Lewes in 1264, where Henry was captured. He was effectively sidelined for a time as Montfort summoned a unique form of parliament. However, royalists rallied, and after Montfort's death at the Battle of Evesham in 1265, Henry's authority was restored.

Henry's marriage to Eleanor of Provence further complicated his reign. While they shared a close relationship and had five children, including the future Edward I, Eleanor was deeply unpopular. She was seen as meddling in English politics, and her Savoyard relatives, whom Henry awarded with lands and titles, were resented by the native nobility.

When Henry III passed away in 1272, he had reigned for 56 years, one of the longest in English history. His legacy was mixed. Though he did champion art and architecture, fostering the growth of Gothic architecture, and maintained the kingdom's stability, his financial mismanagement and favoritism sowed the seeds of political reform.

The English people's sentiments at the time of his death would have been varied. Some saw him as a well-intentioned but weak king, while others were frustrated with his leadership. Yet, upon his death, the transition to his son Edward's rule was smooth, suggesting a level of public acceptance and perhaps hope for a stronger monarchy.

The period saw a rich blend of cultures, with French still being the dominant language of the court but the usage of English increasing in legal and official documents. The thirteenth century was also a period of scholastic and theological exploration, with institutions like Oxford and Cambridge gaining prominence.