Thomas became one of the most important men at the council and in 1439 it was Thomas, helped by the archdeacon of Metz, who delivered the council report in June which led to the deposition of Pope Eugene IV. In the following August, Thomas travelled to Mainz to attend the Imperial Diet, where he defended the council's decision to depose Eugene, and later became one of the men selected to choose a new Pope, Pope Felix IV/V (previously Amadeus VIII, Duke of Savoy). Thomas became one of the main supporters of the new pope, and was rewarded with a provision to the Bishopric of Dunkeld in November 1440.
Thomas became a crucial figure at the council in 1439. He assisted with delivering the council report that led to Pope Eugene IV's deposition. In August, he defended the council's decision to depose Eugene and was chosen as one of the men to select a new pope, Pope Felix IV/V (previously Amadeus VIII, Duke of Savoy). Thomas became a key supporter of the new pope and received a provision for the Bishopric of Dunkeld in November 1440.