In 1645, after the Royalist defeat at the Battle of Naseby, he retired to Paris, where he became a Roman Catholic and worked on his epic poem "Gondibert". That same year he was appointed Emissary to France, and in 1649 was given the symbolic post of treasurer of the colony of Virginia by the exiled Charles II. The following year, he was made lieutenant governor of Maryland, but was captured at sea, imprisoned, and sentenced to death. In July, 1650, he was put on trial for his life, along with others in front of the newly established High Court of Justice. He is said to have been saved by the intervention of John Milton. He spent all of 1651 in the Tower of London, where he continued writing "Gondibert".