William Warham, Archbishop of Canterbury, made Tunstall his chancellor on 25 August 1511, and shortly afterward appointed him rector of Harrow on the Hill. He eventually became a canon of Lincoln (1514) and archdeacon of Chester (1515). Soon thereafter he was employed on diplomatic business by King Henry VIII and Cardinal Wolsey. In 1515, Tunstall was sent to Flanders with Sir Thomas More. It was at Brussels that he would meet Erasmus as well, becoming the intimate friend of both scholars. In 1519 he was sent to Cologne; a visit to Worms (1520–21) gave him a sense of the significance held by the Lutheran movement and its literature.