Fergal Keane talks to Mohsen Sazegara. He was at the heart of Ayatollah Khomeini's regime from the moment the spiritual leader returned to Iran in 1979. Sazegara helped found the now feared Revolutionary Guard. He watched as those who dissented were executed in their hundreds. But then the regime began to turn against him. Following an interrogation in Tehran's notorious Evin Prison, Mohsen Sazegara began to speak out against the Islamic state he had helped create - a dangerous course of action.