Royal: Arthur, Duke of Brittany, 1187-c 1203

Being a royal or noble child in the Medieval world was a dangerous proposition, particularly for heirs to the throne.  There were always others in the family who felt they had a better claim or more of a right to inherit and, with no adults capable of protecting them, such children could become princes and princesses in towers, forgotten by history and perhaps even killed to eliminate their claim to the crown.

Arthur, 1187-c 1203, was the son of Geoffrey Plantagenet and his wife, Constance, Duchess of Brittany in her own right.  Geoffrey was, in his turn, the son of Henry II and Eleanor of Aquitaine.  Thus, Arthur, through his father, had a viable claim to the throne of England as well as the rest of the Plantagenet holdings on the Continent.  Geoffrey died in 1186, while Constance was pregnant with Arthur.  Henry II died in 1189, which left Arthur the heir apparent, though that term wasn't in use at the time.  Richard I intended to make Arthur his heir if he didn't have children of his own marriage, which he never did.  He wanted to marry Arthur to the daughter of Tancred of Sicily but Tancred's death scuttled that plan.  Richard was busy with the Third Crusade and was later captured by Leopold of Austria, so Arthur's future was on hold.  Constance tried to arrange a marriage between her son and the daughter of Phillip II of France but a knight in the service of John, Ranulf, Earl of Chester, kidnapped Arthur and his mother on their way to negotiate the marriage. 

Richard was able to rescue Arthur and his mother and again declared Arthur his heir.  This was technically correct.  Geoffrey was older than John and his son would have a more senior claim.  However, in those days, royal and noble titles wen to anyone who could fight to gain and keep them, regardless of birth order.  Richard's life was cut short by an unlucky arrow shot in 1199 and John wouldn't be denied the prizes he'd sought for so long, King of England, Duke of Normandy and ruler of the Plantagenet empire.  Arthur was 12 years old and on the verge of what the Medieval world would have considered adulthood, although still young and weak.  He promptly performed homage to King Phillip for Brittany and for the Plantagenet lands in France on condition that Phillip back his claim to the English throne.  John again intervened, ordering the arrest of Constance of Brittany and Arthur.  They escaped and fled to Phillip's dominions.

Then, in 1200, John and Phillip agreed the Treaty of Le Goulet, which called for Phillip to recognize John as Richard's heir and King of England.  John would recognize Phillip as his overlord for the domains in France, with the exception of Brittany.  For a payment of 20,000 marks, John retained suzerain rights over Brittany and thus jurisdiction over Constance and Arthur.  Arthur and John at first mended fences, but by 1202, Arthur was negotiating his own marriage to Marie of France, Phillip's daughter.  Poitou revolted in favor of Arthur, who laid siege to Eleanor of Aquitaine in the Chateau de Mirabeau.  On July 31, 1202, John marched to his mother's rescue at Mirabeau and took Arthur captive, placing him in the Chateau of Falaise in Normandy.

Arthur was put under the custody of Hubert de Burgh, who at first treated him kindly enough.  In 1203, Arthur was transferred to Rouen under the custody of William de Braose, where he soon after disappeared.  Stories mounted that John himself killed Arthur and ordered his body dumped in the Seine.  William de Braose was also accused of having killed Arthur at John's order.  How, why and when Arthur died will forever remain a mystery.  His sister Eleanor remained a prisoner of her uncle in England, never having a family or being able to rule Brittany in her own right.  That privilege passed to Arthur and Eleanor's half-sister Alys, Constance's daughter by a subsequent marriage.  Arthur features in Shakespeare's play, The Life and Death of King John.  He also figures in alternative histories in which the Plantagenet line survives and continues to rule England in modern times.