Roger Mortimer: The Greatest Traitor Who Ruled as King

Written by Simon Williams

Roger Mortimer stands out in the history of medieval England not simply as a rebel or a lover, but as a man who briefly held the English crown in all but name. His story is one of the most dramatic of the fourteenth century: a fall from power, a dramatic escape from the Tower of London, a triumphant return, and an eventual execution ordered by the very king he had helped to raise.

Origins and Early Career

Roger Mortimer was born around 1287 into one of the most powerful Marcher lord families in England. The Mortimers held vast estates along the Welsh border, and Roger inherited that tradition of military command and political ambition. He served in Scotland and Ireland, proving himself a capable military commander, and by the reign of Edward II he had become one of the leading magnates of the realm.

Opposition to Edward II

Edward II's reign was defined by favouritism and political incompetence. His reliance first on Piers Gaveston and later on the Despensers alienated the powerful barons who expected to share in royal governance. Mortimer became a central figure in the baronial opposition. In 1321, he joined the coalition of lords that forced Edward to exile the Despensers.

But Edward recovered. The Despensers returned. In 1322, after the defeat of the barons at the Battle of Boroughbridge, Mortimer was captured. He was sentenced to death, but the sentence was commuted to life imprisonment in the Tower of London.

The Escape from the Tower

In August 1323, Roger Mortimer accomplished something almost without precedent: he escaped from the Tower of London. The details remain somewhat murky, but it appears his guards were drugged and he was lowered by rope from a window to waiting allies. He fled to France, where he found refuge at the court of Charles IV.

It was in France that he encountered Isabella, Queen of England, who had been sent to negotiate with her brother the French king. Their relationship became intimate, and together they formed the plan that would transform England.

The Invasion and Fall of Edward II

In September 1326, Mortimer and Isabella landed in Suffolk with a small invasion force. Edward II's support collapsed with remarkable speed. The Despensers were captured and executed. Edward II fled west and was eventually captured in Wales in November 1326.

Mortimer now effectively ruled England alongside Isabella. Edward II was imprisoned at Berkeley Castle and died there in September 1327 under circumstances that have been debated ever since. The official account was natural causes, but contemporaries and later historians have suspected murder, and Mortimer's role in whatever occurred remains a matter of historical controversy.

The Regency and the Acquisition of Power

The new king, Edward III, was fourteen years old. Real power lay with his mother and Mortimer. Mortimer accumulated titles, lands, and wealth at a rate that alarmed the nobility. He was created Earl of March in 1328, a new title signalling a claim to near-royal status.

The Treaty of Edinburgh in 1328, which recognised Scottish independence and Robert Bruce as king, was deeply unpopular in England and seen as a humiliation. It became known derisively as the Shameful Peace. Mortimer's handling of a subsequent rebellion by Henry of Lancaster, and the suspicious death of Edward II's brother the Earl of Kent, further eroded his support among the nobility.

The Coup at Nottingham Castle

Edward III endured Mortimer's dominance until he was ready to act. In October 1330, the young king and a group of allies entered Nottingham Castle through a secret passage and arrested Mortimer in Isabella's chamber. The speed and decisiveness of the act reflected how carefully it had been planned and how completely Mortimer had been caught off guard.

Mortimer was taken to London, tried before Parliament, and condemned to death. He was hanged at Tyburn in November 1330. He was around forty-three years old. Isabella was spared; Edward III treated his mother with respect despite her role in the regency, though she was effectively retired from political life.

Historical Legacy

Mortimer's reputation has fluctuated across the centuries. He was long cast as a villain, the adulterous usurper who destroyed a king and exploited a boy monarch. More recent assessments have placed him within the context of baronial politics and acknowledged his genuine ability as a military commander and administrator.

What is beyond dispute is the drama of his life. Few figures in medieval England rose so high so rapidly, or fell so completely. His escape from the Tower, his conquest of England with a foreign army, his years of dominance, and his sudden overthrow by the teenage king he had underestimated form a narrative that reads almost like fiction.

Roger Mortimer was the product of his age: an age when great lords expected to govern alongside their kings, when the line between legitimate counsel and usurpation was easily crossed, and when political survival required not just ambition but constant vigilance. He possessed the first in abundance. At the end, he lost the second.

To understand Mortimer fully, his story must be read alongside that of Queen Isabella of France, whose own trajectory from discarded queen to regent is one of the most remarkable in medieval history. For the broader context of Edward II's troubled reign, our article on Edward II traces the political crisis from its origins.

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