From the Daily Mail:
The Catholic church was thrown into turmoil today after Pope Benedict XVI made the shock decision to quit the papacy because of his deteriorating health.
In a decision that has surprised even his closest aides, the 85-year-old Pontiff said his strength was 'no longer adequate to continue in office due to his advanced age'.
He announced his resignation in Latin to a meeting of Vatican cardinals this morning, saying he did not have the 'strength of mind and body' to continue leading more than a billion Roman Catholics worldwide.
The decision is unprecedented. He is the first Pope to resign since Gregory XII in 1415 and no Pontiff in history has stepped down on health grounds.