Simon de Montfort, 6th Earl of Leicester in the context of "Eleanor of Provence"

The Battle of Lewes was one of two main battles of the conflict known as the Second Barons' War. It took place at Lewes in Sussex, on 14 May 1264. It marked the high point of the career of Simon de Montfort, 6th Earl of Leicester, and made him the "uncrowned King of England". Henry III's forces left the safety of Lewes Castle and St. Pancras Priory to engage the barons in battle and were initially successful, with Henry's son Prince Edward routing part of the baronial army with a cavalry charge. However, Edward pursued his quarry off the battlefield and left Henry's men exposed. Henry was forced to launch an infantry attack up Offham Hill where he was defeated by the barons' men defending the summit. The royalists fled back to the castle and priory and the King was forced to sign the Mise of Lewes, ceding many of his powers to de Montfort.

The Second Barons' War (1264–1267) was a civil war in England between the forces of barons led by Simon de Montfort against the royalist forces of King Henry III, led initially by the king himself and later by his son, the future King Edward I. The barons sought to force the king to rule with a council of barons, rather than through his favourites. The war also involved a series of massacres of Jews by some of de Montfort's supporters (and his sons Henry and Simon) in attacks aimed at seizing and destroying evidence of baronial debts. To bolster the initial success of his baronial regime, de Montfort sought to broaden the social foundations of parliament by extending the franchise to the commons for the first time. However, after a rule of just over a year, de Montfort was killed by forces loyal to the king at the Battle of Evesham.

The Battle of Evesham (4 August 1265) was one of the two main battles of 13th century England's Second Barons' War. It marked the defeat of Simon de Montfort, Earl of Leicester, and the rebellious barons by the future King Edward I, who led the forces of his father, King Henry III. It took place on 4 August 1265, near the town of Evesham, Worcestershire.

With the Battle of Lewes, de Montfort had won control of royal government, but after the defection of several close allies and the escape from captivity of Prince Edward, he found himself on the defensive. Forced to engage the royalists at Evesham, he faced an army twice the size of his own. The battle soon turned into a massacre; de Montfort himself was killed and his body mutilated. It was described by the contemporary historian Robert of Gloucester as the "murder of Evesham, for battle it was none". Though the battle effectively restored royal authority, scattered resistance remained until the Dictum of Kenilworth was signed in 1267.

The House of Lancaster was a cadet branch of the royal House of Plantagenet. The first house was created when King Henry III of England created the Earldom of Lancaster—from which the house was named—for his second son Edmund Crouchback in 1267. Edmund had already been created Earl of Leicester in 1265 and was granted the lands and privileges of Simon de Montfort, 6th Earl of Leicester, after de Montfort's death and attainder at the end of the Second Barons' War. When Edmund's son Thomas, 2nd Earl of Lancaster, inherited his father-in-law's estates and title of Earl of Lincoln he became at a stroke the most powerful nobleman in England, with lands throughout the kingdom and the ability to raise vast private armies to wield power at national and local levels. This brought him—and Henry, his younger brother—into conflict with their cousin King Edward II, leading to Thomas's execution. Henry inherited Thomas's titles and he and his son, who was also called Henry, gave loyal service to Edward's son King Edward III.

The second house of Lancaster was descended from John of Gaunt, a Plantagenet prince, who married the heiress of the first house, Blanche of Lancaster. Edward III married all his sons to wealthy English heiresses rather than following his predecessors' practice of finding continental political marriages for royal princes. Henry of Grosmont, 1st Duke of Lancaster, had no male heir so Edward married his son John to Henry's heiress daughter and John's third cousin Blanche of Lancaster. This gave John the vast wealth of the House of Lancaster. Their son Henry usurped the throne in 1399, creating one of the factions in the Wars of the Roses. There was an intermittent dynastic struggle between the descendants of Edward III. In these wars, the term "Lancastrian" became a reference to members of the family and their supporters. The family provided England with three kings: Henry IV (r. 1399–1413), Henry V (r. 1413–1422), and Henry VI (r. 1422–1461 and 1470–1471).

Edmund Crouchback (16 January 1245 – 5 June 1296) was a member of the royal Plantagenet Dynasty and the founder of the House of Lancaster. He was Earl of Leicester (1265–1296), Lancaster (1267–1296) and Derby (1269–1296) in England and Count Palatine of Champagne (1276–1284) in France.

Named after the 9th-century saint, Edmund was the second surviving son of King Henry III of England and Eleanor of Provence and the younger brother of King Edward I of England, to whom he was loyal as a diplomat and warrior. In 1254, the 9-year-old Edmund became involved in the "Sicilian business", in which his father accepted a papal offer granting the Kingdom of Sicily to Edmund, who made preparations to become king. However, Henry III could not provide funds for the operation, prompting the Papacy to withdraw the grant and give it to Edmund's uncle, Charles I of Anjou. The "Sicilian business" outraged the barons led by the Earl of Leicester and Edmund's uncle, Simon de Montfort, 6th Earl of Leicester, and was cited as one of the reasons for limiting Henry's power. Deterioration of relations between the barons and the king resulted in the Second Barons' War, in which the royal government, supported by Edmund, triumphed over the baronage following the death of Montfort in the Battle of Evesham in 1265.

Evesham Abbey was founded by Saint Egwin at Evesham in Worcestershire, England between 700 and 710 following an alleged vision of the Virgin Mary by a swineherd by the name of Eof.

According to the monastic history, Evesham came through the Norman Conquest unusually well, because of a quick approach by Abbot Æthelwig to William the Conqueror. The abbey is of Benedictine origin, and became in its heyday one of the wealthiest in the country. Simon de Montfort (1208–1265) is buried near the high altar of the ruined abbey, the spot marked by an altar-like memorial monument dedicated by the Archbishop of Canterbury in 1965.

Eleanor de Montfort, Princess of Wales and Lady of Snowdon (1252 – 19 June 1282) was an English noblewoman and Welsh princess through her marriage to Llywelyn ap Gruffudd, who was Prince of Gwynedd, and later, Prince of Wales. She was the daughter of Simon de Montfort, 6th Earl of Leicester and Eleanor of England. She was also the second woman who can be shown to have used the title Princess of Wales.

The House of Montfort was a medieval French noble house that eventually found its way to the Kingdom of England and originated the famous Simon de Montfort, 6th Earl of Leicester. However, his father, Simon de Monfort the Elder, who led the French Crusaders during the Albigensian Crusade, is far more notorious in France and among military medievalists.

The family began when Hugh Capet granted a petty lordship to Guillaume de Montfort in the Île-de-France. His successors were to be the vassals of the counts of Beaumont. Guillaume's son, Amaury began building a castle that would eventually become the eponymous Montfort-l'Amaury. The project, however, was incomplete when he died c. 1053, but his son, Simon, finished it in 1067. His great-grandson, Simon IV would eventually marry the heiress of Leicester, and their son, Simon V would become the first Montfort earl of Leicester.