On 18 March 1333, Edward was invested with the earldom and county of Chester, and in the parliament of 9 February 1337 he was created Duke of Cornwall and received the duchy by charter dated 17 March. This is the earliest instance of the creation of a duke in England. By the terms of the charter the duchy was to be held by him and the eldest sons of kings of England. His tutor was Dr. Walter Burley of Merton College, Oxford. His revenues were placed at the disposal of his mother in March 1334 for the expenses she incurred in bringing up him and his two sisters, Isabella and Joan. Rumours of an impending French invasion led the king in August 1335 to order that he and his household should remove to Nottingham Castle as a place of safety.