When Queen Anne was near death, Robert Harley and Henry Bolingbroke reached out to the man who would one day be called the Old Pretender and talked about his possible accession to the Throne if he converted. He refused stating, "I have chosen my own course, therefore it is for others to change their sentiments." But what if he hadn't? What if he had agreed to convert to Anglicanism? Would his accession to being king even be possible? He would still have been Catholic at one point so I think legally, he'd still be considered Catholic but who knows? It still seems unlikely to me but it might give him a chance at least of becoming King for real.