Many of the clergy who served under him in Armagh recommended that the Pope appoint Conwell to head the diocese permanently. Some opposed him, accusing him of being frequently absent from his parish to visit France and Scotland. The British government also objected, favoring Patrick Curtis instead, as they saw him as more friendly to their interests. Pope Pius VII appointed Curtis to Armagh, offering Conwell instead a choice of the sees of Philadelphia or Madras; Conwell chose Philadelphia. Now more than 70 years old, he was ordained bishop in London on 24 September 1819, by Bishop William Poynter, the Vicar Apostolic of the London District, assisted by Fathers James Bramston and Joseph Francis Carpue.