ARTHUR I  . (118g–1 203), duke of Brittany, was the posthumous son of Geoffrey, the fourth son of Henry II. of England, and Constance, heiress of Conan IV., duke of Brittany . The Bretons hoped that their young prince would uphold their independence, which was threatened by the English . Henry II. tried to seize Brittany, and in 1187 forced Constance to marry one of his favourites, Randulph de Blundevill, earl of Chester (d . 1232) . Henry, however, died soon afterwards (1189) . The new king of England, Richard Cceur de Lion, claimed the guardianship of the young Arthur, but in 1190 Richard left for the Crusade . Constance profited by his absence by governing the duchy, and in 1194 she had Arthur proclaimed duke of Brittany by an assembly of barons and bishops . Richard invaded Brittany in 1196, but was defeated in 1197 and became reconciled to Con-stance . On his death in 1189, the nobles of Anjou, Maine and Touraine refused to recognize John of England, and did homage to Arthur, who declared himself the vassal of Philip Augustus . In 1202 war was resumed between the king of England and the king of France . The king of France recognized Arthur's right to Brittany, Anjou, Maine and Poitou .

While Philip Augustus was invading

Normandy, Arthur tried to seize Poitou . But, surprised at Mirebeau, he fell into the hands of John, who sent him prisoner to Falaise . In the following year he was transferred to Rouen, and disappeared suddenly . It is thought that John killed him with his own hand . After this murder John was condemned by the court of peers of France, and stripped of the fiefs which he possessed in France . See Ralph of Coggeshall, " Chronicon Anglicanum," in the Monumenta Britanniae historica; Dom Lobineau, Histoire de Bretagne (1702); Dom Morice, Histoire de Bretagne (1742–1756); A. de la Borderie, Histoire de Bretagne, vol. iii . (1899); Bemont, " De la condamnation de Jean-sans-Terre par la Cour des Pairs de France," in the Revue historique (1886), vol. xxxii .