The image shows Pope Benedict XVI visiting the remains of Pope St Peter Celestine V on a visit to the earthquake town of Sulmona in 2009. Peter Celestine V is interesting because he is the only pope so far in history to have resigned. Although an ascetical and holy man, he allowed himself to be drawn into the papacy, for which he was totally unsuited. When he had created a lot of confusion, he decided to resign. Patrick Duffy puts together what is known about this pope.