Eustace was Lord Chancellor from May 1198 to May 1199. During this time he also acted as a royal justice, and in January 1199, Richard sent him to King Philip II of France to notify the French king that the truce between Philip and Richard was over. With the death of King Richard and the accession of King John of England, Eustace was replaced as chancellor by Hubert Walter, but Eustace was still employed by the king on diplomatic errands, including two errands to the French king, in 1202 and 1204. It was at this time that Pope Innocent III began to use Eustace as a papal judge-delegate, first appointing him to help mediate a dispute between Hubert Walter and the monks of Canterbury.