Arthur I, Duke of Brittany

Arthur was born in 1187, the son of Constance of Brittany and Geoffrey II of Brittany, who died before he was born. As an infant, Arthur was second in line to the succession of his grandfather King Henry II, after his uncle Richard. King Henry died when Arthur was 2 years old, and Richard I became the new king in his place.

While Richard was away on the Third Crusade, Arthur's mother Constance sought to make the Duchy of Brittany more independent. On 11 November 1190, Arthur was named as Richard's heir[1] and was betrothed to a daughter of Tancred of Sicily as part of their treaty.[2] However, Emperor Henry VI conquered the Kingdom of Sicily in 1194, so the betrothal of Arthur came to nothing.

A marriage plan, originally aiming to establish an alliance between King Richard and King Philip II of France to marry Arthur's elder sister Eleanor to Philip's son Louis also failed. In 1196, Constance had the young Arthur proclaimed Duke of Brittany and her co-ruler as a child of nine years. The same year, Richard summoned Arthur, as well as his mother Constance,[3] to Normandy, but Ranulf de Blondeville, 6th Earl of Chester, stepfather of Arthur, abducted Constance. Richard marched to Brittany to rescue Arthur, who was then secretly carried to France to be brought up with Louis.

Arthur paying homage to Philip II of France. Chroniques de St Denis, British Library.

When Richard died on 6 April 1199, on his deathbed he proclaimed his brother John as his heir, fearing Arthur was too young to look after the throne. Arthur was only twelve years old at the time and under the influence of the French king. John immediately claimed the throne of England, but much of the French nobility were resentful at recognising him as their overlord. They preferred Arthur, who declared himself vassal of Philip. Philip recognised Arthur's right to Anjou, Maine, and Poitou. Upon Richard's death Arthur led a force to Anjou and Maine.[4] From 18 April, he styled himself as Duke of Brittany, Count of Anjou and Earl of Richmond.

On 18 September, John persuaded the seneschal of Anjou, William des Roches, to defect, claiming Arthur would be a Capetian puppet. Four days later William took Arthur and Constance prisoners to Le Mans. Viscount Aimery, the seneschal appointed by John, took Arthur and Constance and fled the court to Angers, and later the court of Philip II.[5]

The Treaty of Le Goulet was signed by the kings John of England and Philip II of France in May 1200 and meant to settle once and for all the claims the Norman kings of England had as Norman dukes on French lands, including, at least for a time, Brittany. Under the terms of the treaty, Philip recognised John as King of England as heir of his brother Richard I and thus formally abandoned any support for Arthur. John, meanwhile, recognised Philip as the suzerain of continental possessions of the Angevin Empire.

Philip had previously recognised John as suzerain of Anjou and the Duchy of Brittany, but with this he extorted 20,000 marks sterling in payment for recognition of John's sovereignty of Brittany.[lower-alpha 1]

The Château de Falaise, where Arthur was imprisoned by King John

After the signing of the Treaty of Le Goulet, and feeling offended by Philip, Arthur fled to John, his uncle, and was treated kindly, at least initially. However, he later became suspicious of John and fled back to Angers. Some unidentified source said that in April 1202, Arthur was again betrothed, this time to Marie of France, a daughter of Philip II and Agnes of Andechs-Merania.[6]

After his return to France, and with the support of Philip II, Arthur embarked on a campaign in Normandy against John in 1202. Poitou revolted in support of Arthur. The Duke of Brittany besieged his grandmother, Eleanor of Aquitaine, John's mother, in the Château de Mirebeau. John marched on Mirebeau, taking Arthur by surprise on 31 July 1202.[7] Arthur was captured by John's barons on 1 August, and imprisoned in the Château de Falaise in Falaise, Normandy.

At the Chateau de Falaise, Arthur was guarded by Hubert de Burgh. According to contemporaneous chronicler Ralph of Coggeshall, John ordered two of his servants to blind and castrate the duke. de Burgh could not bring himself to let Arthur be mutilated. Fearful of John, de Burgh leaked news that Arthur had died of natural causes. This news infuriated Brittany, who suspected that Arthur had been murdered.[8] The following year Arthur was transferred to Rouen, under the charge of William de Braose.[9] Arthur vanished in April 1203, in the background of several military victories by King Phillip of France against King John.[9]

Prince Arthur and Hubert de Burgh by William Frederick Yeames, 1882. Manchester Art Gallery.

Arthur's disappearance gave rise to various stories. One account was that Arthur's gaolers feared to harm him, and so he was murdered by John directly and his body dumped in the Seine. The Margam Annals provide the following account of Arthur's death:

After King John had captured Arthur and kept him alive in prison for some time, at length, in the castle of Rouen, after dinner on the Thursday before Easter, when he was drunk and possessed by the devil ['ebrius et daemonio plenus'], he slew him with his own hand, and tying a heavy stone to the body cast it into the Seine. It was discovered by a fisherman in his net, and being dragged to the bank and recognized, was taken for secret burial, in fear of the tyrant, to the priory of Bec called Notre Dame de Pres.[10]

William de Braose was rumoured to have committed Arthur's alleged assassination. He rose high in John's favour after Arthur's disappearance, receiving new lands and titles in the Welsh Marches. Many years after Arthur's disappearance, and just prior to a conflict with King John, de Braose's wife Maud de Braose accused the king of murdering Arthur.[11] Not only the Bretons, but even Philip II, were ignorant of what actually happened, and whether Arthur was alive or dead. Whatever his fate, Arthur left no known issue.

The mystery surrounding Arthur's death complicated his succession. This succession was presumably influenced by both King John and King Philip II.[lower-alpha 2] There were no male heirs to the ducal crown and so his succession as duke was constrained to several choices among his sisters.

His sister Eleanor, the 'Fair Maid of Brittany', was also King John's prisoner. Eleanor also presented a complicating factor, if not a threat, to John's succession plans as King of England. She remained imprisoned for her entire life, through the reign of John's actual successor, his son Henry III of England. While imprisoned, she never married and had no issue. Her imprisonment and the fact that she was located in England made it impossible for her to reign as hereditary Duchess of Brittany.

Arthur I was succeeded by his half-sister, Alix of Thouars, the daughter of Constance and her third husband Guy of Thouars.[lower-alpha 3]

• Carley, James P.; Riddy, Felicity, eds. (1998). Arthurian Literature XVI. D.S. Brewer.CS1 maint: ref=harv (link)
• Everard, J. A. (2004). Brittany and the Angevins: Province and Empire 1158–1203. Cambridge University Press.CS1 maint: ref=harv (link)
• Gillingham, John (1984). The Angevin Empire. Hodder Arnold.CS1 maint: ref=harv (link)
• Legge, M. Dominica (1982), "William the Marshal and Arthur of Brittany", Historical Research, volume 55
• McAuliffe, Mary (2012). Clash of Crowns: William the Conqueror, Richard Lionheart, and Eleanor of Aquitaine. Rowman & Littlefield Publishers, Inc.CS1 maint: ref=harv (link)
• McDougall, Sara (2017). Royal Bastards: The Birth of Illegitimacy, 800-1230. Oxford University Press.CS1 maint: ref=harv (link)
• Powicke, F. M. (October 1909), "King John and Arthur of Brittany", The English Historical Review, volume 24, pp. 659–674
• Seel, Graham E. (2012). King John: An Underrated King. Anthem Press.CS1 maint: ref=harv (link)

Wikimedia Commons has media related to Arthur I of Brittany.

•  "Arthur (duke)" . Encyclopedia Americana. 1920.
• "Arthur (duke)" . New International Encyclopedia. 1905.