BTW - barring a Royal who happens to follow the Roman Catholic faith (or any other faith for that matter), from the from succeeding to the throne, is obviously discriminatory and out of date too.
Not totally, Jan. If the monarch is to remain the head of the Church of England (and I'm not getting into that particular debate here), he or she could NOT be a practising Roman Catholic. That particular rule was introduced for a very good reason; the ensuring that no future monarch could pull England (as it was at the time) back into the arms of the Papacy.
I'd agree that this was probably a heavy-handed approach, but that was the underlying reason.