the Welsh were allowed to maintain their own customary laws in some cases of property disputes. After 1277, and increasingly after 1283, Edward embarked on a project of English settlement of Wales, creating new towns like Flint, Aberystwyth and Rhuddlan. Their new residents were English migrants, the local Welsh being banned from living inside them, and many were protected by extensive walls. An extensive project of castle-building was also initiated, under the direction of James of Saint George, a prestigious architect whom Edward had met in Savoy on his return from the crusade. These included the Beaumaris, Caernarfon, Conwy and Harlech castles, intended to act both as fortresses and royal palaces for the King. His programme of castle building in Wales heralded the introduction of the widespread use of arrowslits in castle walls across Europe, drawing on Eastern architectural influences. Also a product of the Crusades was the introduction of the concentric castle, and four of the eight castles Edward founded in Wales followed this design. The castles drew on imagery associated with the Byzantine Empire and King Arthur in an attempt to build legitimacy for his new regime, and they made a clear statement about Edward's intention to rule Wales permanently. In 1284, King Edward had his son Edward (later Edward II) born at Caernarfon Castle, probably to make a deliberate statement about the new political order in Wales. David Powel, a 16th-century clergyman, suggested that the baby was offered to the Welsh as a prince "that was borne in Wales and could speake never a word of English", but there is no evidence to support this widely reported account. In 1301 at Lincoln, the young Edward became the first English prince to be invested with the title of Prince of Wales, when the King granted him the Earldom of Chester and lands across North Wales. The King seems to have hoped that this would help in the pacification of the region, and that it would give his son more financial independence. Diplomacy and war on the Continent Edward never again went on crusade after his return to England in 1274, but he maintained an intention to do so, and in 1287 took a vow to go on another Crusade. This intention guided much of his foreign policy, until at least 1291. To stage a European-wide crusade, it was essential to prevent conflict between the sovereigns on the Continent.