The Siege of Kenilworth Castle

How Henry III’s assault on Kenilworth Castle, which began on 25 June 1266, turned into the longest siege in English medieval history.

A reconstruction of Kenilworth Castle as it may have looked just before the siege of 1266. King John, Henry III’s father, had added the outer stone walls and greatly enlarged the mere, or lake, surrounding the castle in the early 13th century
A reconstruction of Kenilworth Castle as it may have looked just before the siege of 1266. King John, Henry III’s father, had added the outer stone walls and greatly enlarged the mere, or lake, surrounding the castle in the early 13th century © Historic England (illustration by Stephen Conlin)

WAR WITH THE BARONS

In the mid-1260s England was divided by civil war. Henry III, who had been on the throne since 1216, was at loggerheads with some of his leading nobles, who wanted to curb his power. Their leader was the king’s brother-in-law, Simon de Montfort, Earl of Leicester, who defeated the king’s forces at the Battle of Lewes in 1264. He held the king captive for 15 months before he was himself defeated and killed in August 1265 at the Battle of Evesham by Henry’s son, the future Edward I.

Many of Montfort’s supporters fought on after his death, and Henry had to deal with uprisings across the country. The rebels had one key asset: Kenilworth Castle. This mighty fortress, lying at the heart of England, was one of the largest in the kingdom. It had been a royal castle, and King John, Henry’s father, had spent vast sums strengthening and expanding its outer defences, which included a giant mere or lake. In 1253 Henry III had given it to Montfort for life, probably hoping to secure his loyalty. 

The death and mutilation of Simon de Montfort at the Battle of Evesham, depicted in an early 14th-century manuscript
The death and mutilation of Simon de Montfort at the Battle of Evesham, depicted in an early 14th-century manuscript. He met a grisly end, struck through the neck by a lance, and his corpse was then brutally dismembered. His body parts were despatched around the kingdom as a warning to potential rebels © British Library Board (Cotton Nero D.II fol 177)

PREPARING FOR SIEGE

By giving away one of his most heavily fortified castles, Henry had taken a huge risk – as soon became apparent after Evesham, when it became a focus for resistance. Although Montfort’s son, also called Simon, promised to give Kenilworth back to the king, his father’s supporters inside the castle had other ideas. Henry attempted to persuade the garrison to surrender, but they refused all his overtures. His patience finally snapped after his messenger to them in March 1266 returned with a severed hand. The only way for Henry to reclaim the castle was by force.

By the time the royal forces assembled at Kenilworth Castle, the garrison – who probably numbered about 1,200, including wives, children and servants – had built up stocks of enough food to hold out for months. They had managed to obtain siege engines, according to a contemporary chronicler, ‘hitherto unheard of among us and unseen’. Determined to retake the castle, the king had also amassed a huge arsenal of weaponry – including 2,000 wooden ‘hurdles’ (presumably screens to protect the royal soldiers from missiles), 60,000 crossbow bolts and nine siege engines.  

In this 14th-century illustration, stone balls are being thrown at a castle by a simple siege engine operated by a counterpoise, like the larger trebuchets used at Kenilworth in 1266. Some of the stone balls thrown by the siege engines at Kenilworth, weighing up to 140 kilos, were found by archaeologists in the 1960s
In this 14th-century illustration, stone balls are being thrown at a castle by a simple siege engine operated by a counterpoise, like the larger trebuchets used at Kenilworth in 1266. Some of the stone balls thrown by the siege engines at Kenilworth, weighing up to 140 kilos, were found by archaeologists in the 1960s © British Library Board (Royal 16 G.VI fol 388)

THE SIEGE BEGINS

On 25 June 1266 an all-out siege began. The king’s stone-throwing machines, erected all around the castle, bombarded it with a continuous stream of missiles. They were thwarted, however, by the superior range of the weaponry inside – one chronicler described the stone projectiles from the two sides ‘clashing in the air’. The king had to send to London for larger machines. One of his wooden siege towers, apparently containing 200 crossbowmen and attached to the walls of the castle, was rendered useless by a well-aimed missile.

The water defences were preventing the royal forces from undermining the castle walls, so the king had barges hauled overland from Chester for a waterborne assault across the mere. But the defenders managed to repel them.

Kenilworth Castle from the south-west
Kenilworth Castle from the south-west. At the time of the siege, the area in the foreground was covered by the mere, which prevented the king’s forces from getting close enough to undermine the walls

LAST STAND

Henry, by now desperate to restore his prestige and authority, called a parliament near the castle in October, which resulted in the peace terms known as the Dictum of Kenilworth, issued on 31 October. This allowed for the rebels to regain their forfeited lands on payment of heavy fines. However, the garrison rejected these conditions as too harsh, and vowed to fight on.

The siege wore on for a further six weeks. But in the end, as Henry ordered further forces to prepare to storm the castle, disease and starvation brought about what the siege had failed to. On 13 December the remnants of the garrison submitted to the terms they had been offered in October. They were allowed to leave with their arms, horses and harness. Only two days’ supply of food remained in the castle.

 

The bronze effigy of Henry III on his tomb in Westminster Abbey. Henry died in 1272, six years after the siege of Kenilworth
The bronze effigy of Henry III on his tomb in Westminster Abbey. Henry died in 1272, six years after the siege of Kenilworth © Angelo Hornak/Alamy

THE SIEGE’S OUTCOME

At 172 days, Kenilworth’s was the longest siege in English medieval history. What did it achieve?

For Henry, Kenilworth Castle was at least restored to him. He immediately gave it to his younger son, Edmund, who was made Earl of Lancaster the following year – so beginning about 200 years of the castle’s ownership by the House of Lancaster.

In terms of establishing peace, however, the siege achieved little. The victorious royalists behaved vindictively towards their opponents, who quickly started up trouble elsewhere. When the civil war between Henry and his barons finally ended nearly a year later, it was the result of political compromise.

The siege was also ruinously expensive, leaving Henry so short of money that he had to pawn the jewels from the shrine of King Edward the Confessor in Westminster Abbey.

But perhaps the siege’s greatest impact was on the young Lord Edward, who succeeded his father in 1272 as Edward I. At Kenilworth Castle he had seen the full array of the latest weaponry pitted against a formidable modern fortress, in a type of warfare refined by crusaders in the Middle East and in the gruelling conflict between the Plantagenets and the kings of France. It may well have been this direct experience of how castles worked that informed his thinking in time for the crusades he embarked on in 1270 and his great castle-building (and besieging) campaigns from 1277 onwards in Wales and Scotland.

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