IT ISN’T as though Istanbul lacked mosques. At evening, the skyline of minarets piercing the dusk is haunting and unforgettable. President Erdoğan’s decision that Muslim prayer will begin again next week at Ayasofya, Hagia Sophia, has caused deep distress for the Christian minority in Turkey and for the whole Orthodox world (News, 19 June). The Pope has also expressed sadness.

Hagia Sophia — “Holy Wisdom” — was once the greatest church in Christendom: it was built by the Emperor Justinian in the sixth century, who apparently said at the conclusion of the work, “Solomon, I have outdone thee.”

For nearly 1000 years, it was a symbol of Christian civilisation. Eastern scholarship, asceticism, and diplomacy were a beacon of hope for Western Christians during the “Dark Ages”. When Sultan Mehmet II conquered Constantinople in 1453, the church was way past its glory days. The Sultan’s immediate act on entering it was to bow to the ground and give thanks to God. The fall of Constantinople to the Seljuk Turks was a huge shock to the rest of the Christian world.

President Erdoğan’s decision is in tune with his strategy for turning Turkey into a leading Islamic power. It also delivers a blow to Turkish secularists, those who uphold the legacy of Kemal Atatürk, who turned Hagia Sophia into a museum in 1935. President Erdoğan is also aiming at the West, our Christian and secular heritage, and, perhaps, at the casual tourism which has made Hagia Sophia a must-see site for millions of visitors a year.

World-heritage experts have expressed fear for the priceless Christian mosaics in these days of Islamist iconoclasm. I cannot believe that President Erdoğan will want to lose the income and prestige that they bring. But Christians, now, will come as guests of an Islamic state, not as pilgrims, revisiting part of their own past.

I have visited Hagia Sophia on several occasions. I have always found it overwhelming, not least because, while it has been a museum, the stages of its history have been accessible to everyone equally. Christian and Muslim history speak to one another. Justinian’s pride meets Sultan Mehmet’s humility. When I heard the news last week, I was shocked at my grief. I felt that I was losing part of my personal heritage, my link to the creeds and councils that still form our faith.

After the Muslim conquest, the dome mosaic of Christ Pantocrator was covered and later replaced with Islamic calligraphy. It was no accident that the words echo the most beautiful of Qur’anic texts: the “light” sura, asserting that God alone is the light of heaven and earth. Yet the Christian mosaics of the four seraphim surrounding the dome were left. I hope that such moderation is not a thing of the past. After all, the light is one, and we all live beneath the same dome of heaven.