On arriving in Oxford, Vermigli began lecturing on 1 Corinthians, denouncing Catholic doctrines of purgatory, clerical celibacy, and lenten fasting. He then spoke against the Catholic doctrine of the Eucharist, the most sensitive area of disagreement between Protestants and Catholics in England at the time. Conservative faculty, led by Smyth, challenged Vermigli to defend his views in a formal disputation. Smyth fled to St Andrews and finally to Leuven before the disputation could be held, so three Catholic divines, William Tresham, William Chedsey and Morgan Phillips, stepped forward to take his place. The disputation was held in 1549 before Richard Cox, the University Chancellor and a firm Protestant. It focused on the doctrine of transubstantiation, with Vermigli's opponents arguing for it and him against. Chancellor Cox made it obvious that he considered Vermigli to have the better argument, but did not formally declare a winner. The disputation put Vermigli at the forefront of debates over the nature of the Eucharist.