Shock as Pope Benedict XVI resigns

Pope Benedict XVI is to resign at the end of this month after nearly eight years as the head of the Catholic Church, saying he is too old to continue at the age of 85.

The unexpected development - the first papal resignation in nearly 600 years - surprised governments, Vatican-watchers and even the his closest aides.

The then Cardinal Joseph Ratzinger became Pope after John Paul II's death.

The BBC's Alan Johnston reports.