In 1252, on the death of his mother, Blanche of Castile, Alphonse was joint regent with
Charles of Anjou until the return of Louis IX. During that time he took a great part in the campaigns and negotiations which led to the
Treaty of Paris in 1259, under which King
Henry III of England recognized his loss of continental territory to
France (including
Normandy,
Maine,
Anjou, and
Poitou) in exchange for France withdrawing its support for English rebels. was formed of those of France (left) and Castile (right), representing his father and mother respectively:
Per pale azure semé-de-lis or dimidiating gules semé of castles or Aside from the crusades, Alphonse stayed primarily in Paris, governing his estates by officials, inspectors who reviewed the officials' work, and a constant stream of messages. His main work was on his own estates. There he repaired the effects of the
Albigensian war and made a first attempt at administrative centralization, thus preparing the way for union with the crown. On 8 October 1268, Alphonse had all Jews throughout his lands arrested and their property confiscated. When Louis IX formed the
Eighth Crusade, Alphonse again raised a large sum of money and accompanied his brother. This time, however, he did not return to France, dying while on his way back, at
Savona in Italy, on 21 August 1271. ==Death and legacy==