Mosul was already ancient when Christians first settled there in the 2nd century. It stands on the Tigris, one of the rivers that watered the Fertile Crescent and on whose banks some of the oldest civilisations in the world were established. Across the river stood the proud city of Nineveh, capital of the Assyrian Empire, where Sennacherib built a great palace in about 700BCE - you can see his magnificent palace reliefs in the British Museum.
Mosul played a central part in the growth of Christianity in early times. By the 6th century, it was a bishopric of the Assyrian (Chaldean) Church. Some of the world's oldest Christian communities were founded in what is now Iraq, and the valley of the Tigris was home to many of them. Christians were indigenised there before Islam arrived. And when it did, a modus vivendi enabled Christians and Muslims for most of the subsequent centuries to live peaceably together.
These ancient Christian communities harmed no one, did not subvert Islam, did not antagonise their Muslim neighbours. On the contrary, their members were exemplary citizens, aware of their minority status in an Islamic environment but respected as adherents of a fellow Abrahamic faith, a people of the book. They did not look for conflict, simply for a safe space in which to practise their faith peacefully as their forebears had done since time immemorial.
The swift arrival of the radical Sunni movement called Isis has changed all that with a viciousness that has surprised the west. Crosses and statues over Christian churches have been toppled. An 1800 year old church has been destroyed. Christians have been warned: 'if you want to stay alive, convert to Islam at once, or pay the Christian tax (protection money) or get out of the city'. Most are fleeing, perhaps never to return. This exodus was already beginning ten years ago as in other places in Iraq; now it is in full spate. Few are left, for this is no place to stay when lives are at such risk. As are those of Shiite Muslims too - something we mustn't forget.
We weep with these exiles who weep beside the waters of Babylon. We pray for them, and as churches in safe, peaceful western Europe, we shall support them through refugee and aid agencies that are working to bring assistance as quickly as they can. They need to know that they can count on us not to forget them in their great need. They need to know that we shall keep their story alive in the media so that the nation is aware of their plight.
But there is something else we must do. It is to resist demonising Islam because of the cruelty of this rogue movement. Isis, like its parent body Al Qaeda, like Boko Haram in Nigeria, is utterly untypical of mainstream Islam. We mustn't allow these terrible events to cloud our response to a noble world faith with its values of dignity, honour and reverence for life. Instead we should make common cause with our Muslim friends and neighbours to denounce violence and terror, and support them as they speak out against the atrocities perpetrated in their name. The more they can do this, the more chance there is that radicalisation will be stanched before its poison gets expressed in bullets and bombs.
I once sat down with a senior imam I'd got to know. He too was a Sunni, from Saudi Arabia, not a westernised Muslim like most I had met. He gave me a copy of the Qur'an in which he had underlined the passages that spoke well of Christians. 'You are among these' he said, pointing to the Cathedral. So I asked him about the passages where Christians are derided or criticised. 'Those are about renegades who deny the Abrahamic faith' he said, 'not loyal, faithful, god fearing people like you.'
I guess that Islam's reading of Christianity is a more complex matter, where so much is coloured by history; but I remember that encounter with warmth. It helped me to understand the respect with which Islam has in its best époques regarded Christianity. This, I think, is more characteristic of it than the bitterness and hatred that each day's headlines seem to underline and which do so much to fuel the Islamophobia that is becoming a worrying aspect of modern western attitudes.