The line of succession to the British throne is chosen prinicipally due to gender and religion. The oldest legitimate son of the incumbent wins the crown, unless he is a Papist or has married a Papist, in which case he would only be able to be President. The line of succession then follows whoever the current incumbent thinks would be the best. Apart from identifying the next monarch, the line of succession is also used to determine the Pope and the successor to Oprah should the need arise.