treat with the Scots ambassador concerning the proposed marriage of Prince Edward with Mary Queen of Scots. In May 1545 he was despatched on an embassy to the emperor, Charles V. He attended the diet of Bourbourg, and on 16 January 1546–7 he was one of those who signed a treaty of peace at Utrecht. He was not named an executor by Henry VIII and consequently was excluded from Edward VI's privy council. He remained at the court of the emperor till June 1548, taking leave of Charles V at Augsburg on the 11th. Thirlby took part in the important debates in the House of Lords in December 1548 and January 1548–9 on the subject of the sacrament of the altar and the sacrifice of the mass. He declared that "he did never allow the doctrine" laid down in the communion office of the proposed first Book of Common Prayer, stating that he mainly objected to the book as it stood because it abolished the "elevation" and the "adoration". When Somerset expressed to Edward VI some disappointment at Thirlby's attitude, the young king remarked, "I expected nothing else but that he, who had been so long time with the emperor, should smell of the Interim." He voted against the third reading of the act of uniformity on 15 January 1548–9, but enforced its provisions in his diocese after it had been passed. On 12 April 1549 he was in the commission for the suppression of heresy, and on 10 November in that year he was ambassador at Brussels with Sir Philip Hoby and Sir Thomas Cheyne. On 29 March 1550 Thirlby resigned the bishopric of Westminster into the hands of the king, who thereupon dissolved it, and reannexed the county of Middlesex, which had been assigned for its diocese, to the see of London. While bishop of Westminster he is said to have "impoverished the church." On 1 April, following his resignation of the see of Westminster, he was constituted bishop of Norwich. Bishop Burnet intimates that Thirlby was removed from Westminster to Norwich, as it was thought he could do less mischief in the latter see, "for though he complied as soon as any change was made, yet he secretly opposed everything while it was safe to do." In January 1550–1 he was appointed one of the commissioners to correct and punish all anabaptists, and such as did not