In 1067, St Peter Damian, cardinal-bishop of Ostia and a key member of the reform party in Rome, travelled to Florence, where the monks of the neighbouring monastery of Vallombrosa, under the leadership of Giovanni Gualberto, had accused Bishop Pietro Mezzabarba of simony, and had launched a very public campaign against him. Although he had no sympathy for simonists, Damian concluded that the Vallombrosans had not made their case against the bishop,...