Do Christians have a future in the Arab world? It's a question raised with a new sense of urgency as an extraordinarily violent brand of jihadi extremism sweeps through Syria and Iraq. Tens of thousands of Christians, along with other minorities, have been forced from their homes, hundreds murdered. Right across the region Christians are fearful. Stephen Sackur's guest is Bishop Angaelos of the Egyptian Coptic Church. What can the outside world do to protect the Arab Christian tradition?