The Siege of Kenilworth

June 25 - December 13, 1266

The longest recorded siege in England’s history, the Siege of Kenilworth was the last desperate holdout of the rebel forces of the Second Barons’ War (1264 - 1267) against King Henry III after their leader, Simon de Montfort, was killed and dismembered at the Battle of Evesham.

Lasting from June to December of 1266, the siege was the result of a power struggle between King Henry and his Barons, who sought reprieve from his costly choices as King. De Montfort was the de-facto Baronial figurehead and brother-in-law to King Henry, which made the conflict personal as well as political. 

Setting the stage

Henry III is crowned king at the age of 9

King Henry III was crowned King of England in October of 1207 after his father, King John, died of dysentery while in the middle of a Baronial feud. Some say he was poisoned, but this was never confirmed. Those critical of King Henry’s choices as monarch blame his foolish and costly actions as ruler on his ascension to the throne at such a young age.

Similar to his father, King Henry spent much of his reign quarreling with his barons, who sought to curb his power. Frustrated with Henry’s costly and inept rule, his Barons sought reprieve from expensive wars, high taxes, and foreign dependence through the Provisions of Oxford.

Provisions of Oxford

The Provisions of Oxford were enacted in 1258 and were considered England’s first written constitution. The provisions put forward a plan of reform that exchanged grants from nobility to the Crown (which was bankrupt at the time) for joint control of the government through a Baronial council.

The provisions were created by a group of barons led by Simon de Montfort (pictured) and signed by King Henry. The barons hoped the provisions would curb the King’s power and allow them to have input into how the country was governed.

After just three years, King Henry overturned the provisions with the help of a papal bull (a public decree issued by the office of the Pope). This disregard for their rights didn’t sit well with the nobility, and sparked the start of the Second Barons’ War (1264 - 1267).

Battle of Lewes

Led by Simon de Montfort, rebel forces began a campaign that captured much of southeastern England in the following years, culminating in the Battle of Lewes in May 1264.

During the battle, De Montfort’s forces gained the high ground and defeated the royal army, capturing King Henry and his son, Prince Edward. They were held captive for 15 months with De Montfort effectively ruling England for this time, reducing Henry to little more than a figurehead.

Prince Edward eventually escaped captivity in 1265, and raised an army to engage De Montfort and free his father.

Battle of Evesham

Prince Edward and Simon de Montfort met again at the battle of Evesham in August 1265. After rallying support for the King, Prince Edward raised an army of an estimated 12,000 men, outnumbering De Montfort’s army 2 to 1.

After a valiant effort by De Montfort and his men, the battle turned into a massacre for the rebel forces, with both De Montfort and his son Henry being killed, along with most of their army.

De Montfort met a grisly end. Killed by a lance through the neck, his body was dismembered and his remains were sent to other rebels as a warning.

The remaining rebels (an estimated 1,000 men) retreated to Kenilworth Castle, which was given to De Montfort by King Henry in 1253. De Montfort was married to Henry’s sister, Eleanor of England.

The Siege

Ostracism of the rebels

De Montfort’s supporters fought on after his death, and continued to cause problems for the crown. In the fall of 1265, King Henry stripped the remaining rebels of their lands and titles. They were also excommunicated from the catholic church in July of 1266 by Cardinal Ottobuono (later Pope Adrian V) at the request of King Henry.

Together, these two acts of ostracism put the rebels in a truly desperate position, and set the stage for the longest siege in England’s history.

Royal forces gather at Kenilworth

King Henry attempted to negotiate with the rebels for several months in hopes of avoiding further conflict and cost to the Crown. The rebels forcefully rejected the King’s parley, sending a royal messenger back to Henry with a severed hand.

Out of options, King Henry began raising an army to take the castle back by force.

Rebel weapons kept the royal forces at bay

By the time the King’s forces arrived at Kenilworth in the spring of 1266, the rebels had built up stockpiles of food and weapons for the force of an estimated 1,200 garrisoned in the castle.

The King’s army of 6,000 greatly outnumbered the rebels, but despite their size advantage, their attempts to seize the castle were unsuccessful. The castle was surrounded by a large mere (a defensive wetland) that kept the royal siege engines tasked with breeching the outer walls too far away to be effective. Ironically, it was King Henry’s own father, King John, who expanded the castle and built the mere and formidable curtain walls.

The rebel’s arsenal was specifically built to defend the castle, and proved superior to the King’s. The scale of the rebel’s siege engines was described by an observer as “unseen or unheard of.” These powerful weapons propelled 300-pound stone projectiles far enough to reach and decimate the royal army some 350 yards away.

Humiliated by the superior rebel arsenal, King Henry was forced to send for reinforcements from London, which was tremendously expensive. Larger and stronger siege engines and floating barges were used in an attempt to get close to the castle, both of which were quickly destroyed by the rebels.  

Rebel surrender

The siege continued throughout the summer without success, and by October of 1266 King Henry was desperate to reassert his authority over the rebels and restore his control of the region.

King Henry called a parliament to Kenilworth to draw up peace terms he hoped would end the conflict. The treaty he proposed to the rebels levied heavy fines in exchange for surrender and return of their fortified lands and titles. The rebel barons felt the terms were too harsh and refused them. Fighting continued for another six weeks until disease and starvation forced the rebels to surrender.

On December 13th, 1266, the rebels surrendered under the terms of the treaty offered in October, which became known as the Dictum of Kenilworth. The Dictum allowed the barons to buy back their lands from the Crown and walk free from the castle with their arms and horses.

At the end of the siege, only two days of food and supplies remained in the castle.

Outcomes of the siege

The Second Baron’s War continued for another year, ending in 1267. The war ended when the Statute of Marlborough was passed by parliament.

The statute remedied some of the Barons’ grievances and brought reform and reconstruction to England.

The siege nearly bankrupt the crown, leaving King Henry to pawn royal jewels to raise funds.

About the author

Bryan Manis

Bryan is the Founder and President of Tower & Keep. Researcher by day and designer/entrepreneur by night, his vision is to give life to the unseen and forgotten stories all around us.


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Coronation of King Henry III, Commons.Wikimedia, Cotton Vitellius A. XIII

Leicester_Clock_Tower_Simon_de_Montfort_2, Commons.Wikimedia

Battle of Lewes, Commons.Wikimedia

Montfort_Evesham.jpg, Commons.Wikimedia

Dictum of Kenilworth 1265, The National Archives, UK Gov

Statutum de Marleberge,