Melvyn Bragg and guests discuss events surrounding the medieval division of the Christian Church. In 1054, Cardinal Humbert stormed into the Cathedral of Constantinople and charged down the aisle. In his hand was a Papal Bull – a deed of excommunication - and he slammed it down onto the altar. As he swept out of the startled church, the Papal Legate and his entourage stopped at the door and symbolically shook the sullied dust of Eastern Christianity from their Catholic boots. The Pope of Rome had decreed that the Patriarch of Constantinople was denied his place in heaven, and soon afterwards the Patriarch excommunicated the Pope in return.It was the culmination of an argument over a single word in the Nicene Creed - but after a thousand years of being one Church, so began a permanent rift.But what were the real underlying reasons behind the split, what were its effects and why did it take until December 1965 for the excommunications to be finally revoked?With Henrietta Leyser, medieval historian and Fellow of St Peter’s College, Oxford; Norman Housley, Professor of Medieval History at the University of Leicester; Jonathan Shepard, editor of the Cambridge History of the Byzantine Empire.